<PAGE>   1
                                                                     EXHIBIT 4.2

                                                                       Exhibit B


                                 FORM OF WARRANT


THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE HEREOF HAVE
NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
"SECURITIES ACT") OR ANY STATE SECURITIES LAWS AND MAY NOT BE SOLD, TRANSFERRED
OR OTHERWISE DISPOSED OF UNLESS REGISTERED UNDER THE SECURITIES ACT AND UNDER
APPLICABLE STATE SECURITIES LAWS OR GREYSTONE DIGITAL TECHNOLOGY, INC. SHALL
HAVE RECEIVED AN OPINION OF ITS COUNSEL THAT REGISTRATION OF SUCH SECURITIES
UNDER THE SECURITIES ACT AND UNDER THE PROVISIONS OF APPLICABLE STATE SECURITIES
LAWS IS NOT REQUIRED.


                         [CALLABLE] WARRANT TO PURCHASE

                             SHARES OF COMMON STOCK

                                       OF

                       GreyStone Digital Technology, Inc.

                             Expires [May __], 2005

No.: W-__                                           Number of Shares: __________
Date of Issuance: [May __], 2000


               FOR VALUE RECEIVED, subject to the provisions hereinafter set
forth, the undersigned, GreyStone Digital Technology, Inc., a Delaware
corporation (together with its successors and assigns, the "Issuer"), hereby
certifies that [___________________] or its registered assigns is entitled to
subscribe for and purchase, during the period specified in this Warrant, up to
[___________] shares (subject to adjustment as hereinafter provided) of the duly
authorized, validly issued, fully paid and non-assessable Common Stock of the
Issuer, at an exercise price per share equal to the Warrant Price then in
effect, subject, however, to the provisions and upon the terms and conditions
hereinafter set forth. Capitalized terms used in this Warrant and not otherwise
defined herein shall have the respective meanings specified in Section [9]
hereof.

               1. Term. The right to subscribe for and purchase shares of
Warrant Stock represented hereby shall commence on the date of issuance of this
Warrant and shall expire at 5:00 p.m., eastern time, on May __, 2005 (such
period being the "Term").



                                      -1-
<PAGE>   2
               2. Method of Exercise Payment: Issuance of New Warrant: Transfer
and Exchange.

               (a) Time of Exercise. The purchase rights represented by this
Warrant may be exercised in whole or in part at any time and from time to time
during the Term.

               (b) Method of Exercise. The Holder hereof may exercise this
Warrant, in whole or in part, by the surrender of this Warrant (with the
exercise form attached hereto duly executed) at the principal office of the
Issuer, and by the payment to the Issuer of an amount of consideration therefor
equal to the Warrant Price in effect on the date of such exercise multiplied by
the number of shares of Warrant Stock with respect to which this Warrant is then
being exercised, payable at such Holder's election (i) by certified or official
bank check or (ii) if the Registration Statement has not been declared effective
within one year from the date of issuance of this Warrant, by surrender to the
Issuer for cancellation of a portion of this Warrant representing that number of
unissued shares of Warrant Stock which is equal to the quotient obtained by
dividing (A) the product obtained by multiplying the Warrant Price by the number
of shares of Warrant Stock being purchased upon such exercise by (B) the
difference obtained by subtracting the Warrant Price from the Per Share Market
Value as of the date of such exercise, or (iii) by a combination of the
foregoing methods of payment selected by the Holder of this Warrant. In any case
where the consideration payable upon such exercise is being paid in whole or in
part pursuant to the provisions of clause (ii) of this subsection (b), such
exercise shall be accompanied by written notice from the Holder of this Warrant
specifying the manner of payment thereof and containing a calculation showing
the number of shares of Warrant Stock with respect to which rights are being
surrendered thereunder and the net number of shares to be issued after giving
effect to such surrender.

               (c) Issuance of Stock Certificates. In the event of any exercise
of the rights represented by this Warrant in accordance with and subject to the
terms and conditions hereof, (i) certificates for the shares of Warrant Stock so
purchased shall be dated the date of such exercise and delivered to the Holder
hereof within a reasonable time, not exceeding 5 Trading Days after such
exercise, and the Holder hereof shall be deemed for all purposes to be the
Holder of the shares of Warrant Stock so purchased as of the date of such
exercise, and (ii) unless this Warrant has expired, a new Warrant representing
the number of shares of Warrant Stock, if any, with respect to which this
Warrant shall not then have been exercised (less any amount thereof which shall
have been canceled in payment or partial payment of the Warrant Price as
hereinabove provided) shall also be issued to the Holder hereof at the Issuer's
expense within such time.

               (d) Transferability of Warrant. Subject to Section 2(e), this
Warrant may be transferred by a Holder with the consent of the Issuer, which
consent shall not be unreasonably withheld, provided, that such transfer is with
respect to a minimum of 100,000 shares of Warrant Stock. If transferred pursuant
to this paragraph and subject to the provisions of subsection (e) of this
Section 2, this Warrant may be transferred on the books of the Issuer by the
Holder hereof in person or by duly authorized attorney, upon surrender of this
Warrant at the principal office of the Issuer, properly endorsed (by the Holder
executing an assignment in the form attached hereto) and upon payment of any
necessary transfer tax or other governmental charge imposed upon such transfer.
This Warrant is exchangeable at the principal office of the Issuer for Warrants
for the purchase of the same aggregate number of shares of Warrant Stock, each
new Warrant to represent the right to purchase such number of shares of Warrant
Stock as the Holder



                                      -2-
<PAGE>   3
hereof shall designate at the time of such exchange. All Warrants issued on
transfers or exchanges shall be dated the Original Issue Date and shall be
identical with this Warrant except as to the number of shares of Warrant Stock
issuable pursuant hereto.

               (e) Compliance with Securities Laws.

                   (i) The Holder of this Warrant, by acceptance hereof,
               acknowledges that this Warrant or the shares of Warrant Stock to
               be issued upon exercise hereof are being acquired solely for the
               Holder's own account and not as a nominee for any other party,
               and for investment, and that the Holder will not offer, sell or
               otherwise dispose of this Warrant or any shares of Warrant Stock
               to be issued upon exercise hereof except pursuant to an effective
               registration statement, or an exemption from registration, under
               the Securities Act and any applicable state securities laws.

                   (ii) Except as provided in paragraph (iii) below, this
               Warrant and all certificates representing shares of Warrant Stock
               issued upon exercise hereof shall be stamped or imprinted with a
               legend in substantially the following form:

                   THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUABLE UPON
                   EXERCISE HEREOF HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
                   ACT OF 1933, AS AMENDED (THE "SECURITIES ACT") OR ANY STATE
                   SECURITIES LAWS AND MAY NOT BE SOLD, TRANSFERRED OR OTHERWISE
                   DISPOSED OF UNLESS REGISTERED UNDER THE SECURITIES ACT AND
                   UNDER APPLICABLE STATE SECURITIES LAWS OR GREYSTONE DIGITAL
                   TECHNOLOGY, INC. SHALL HAVE RECEIVED AN OPINION OF ITS
                   COUNSEL THAT REGISTRATION OF SUCH SECURITIES UNDER THE
                   SECURITIES ACT AND UNDER THE PROVISIONS OF APPLICABLE STATE
                   SECURITIES LAWS IS NOT REQUIRED.

                   (iii) The restrictions imposed by this subsection (e) upon
               the transfer of this Warrant or the shares of Warrant Stock to be
               purchased upon exercise hereof shall terminate (A) when such
               securities shall have been resold pursuant to an effective
               registration statement under the Securities Act, (B) upon the
               Issuer's receipt of an opinion of counsel, in form and substance
               reasonably satisfactory to the Issuer, addressed to the Issuer to
               the effect that such restrictions are no longer required to
               ensure compliance with the Securities Act and state securities
               laws or (C) upon the Issuer's receipt of other evidence
               reasonably satisfactory to the Issuer that such registration and
               qualification under the Securities Act state securities laws are
               not required. Whenever such restrictions shall cease and
               terminate as to any such securities, the Holder thereof shall be
               entitled to receive from the Issuer (or its transfer agent and
               registrar), without expense (other than applicable transfer
               taxes, if any), new Warrants (or, in the case of shares of
               Warrant Stock, new stock certificates) of like tenor not bearing
               the applicable legend required by paragraph (ii) above relating
               to the Securities Act and state securities laws.



                                      -3-
<PAGE>   4
               (f) Continuing Rights of Holder. The Issuer will, at the time of
or at any time after each exercise of this Warrant, upon the request of the
Holder hereof, acknowledge in writing the extent, if any, of its continuing
obligation to afford to such Holder all rights to which such Holder shall
continue to be entitled after such exercise in accordance with the terms of this
Warrant, provided that if any such Holder shall fail to make any such request,
the failure shall not affect the continuing obligation of the Issuer to afford
such rights to such Holder.

               3. Stock Fully Paid: Reservation and Listing of Shares:
Covenants.

               (a) Stock Fully Paid. The Issuer represents, warrants, covenants
and agrees that all shares of Warrant Stock which may be issued upon the
exercise of this Warrant or otherwise hereunder will, upon issuance, be duly
authorized, validly issued, fully paid and non-assessable and free from all
taxes, liens and charges created by or through Issuer. The Issuer further
covenants and agrees that during the period within which this Warrant may be
exercised, the Issuer will at all times have authorized and reserved for the
purpose of the issue upon exercise of this Warrant a sufficient number of shares
of Common Stock to provide for the exercise of this Warrant.

               (b) Reservation. If any shares of Common Stock required to be
reserved for issuance upon exercise of this Warrant or as otherwise provided
hereunder require registration or qualification with any governmental authority
under any federal or state law before such shares may be so issued, the Issuer
will in good faith use its best efforts as expeditiously as possible at its
expense to cause such shares to be duly registered or qualified. If the Issuer
shall list any shares of Common Stock on any securities exchange or market it
will, at its expense, list thereon, maintain and increase when necessary such
listing, of, all shares of Warrant Stock from time to time issued upon exercise
of this Warrant or as otherwise provided hereunder, and, to the extent
permissible under the applicable securities exchange rules, all unissued shares
of Warrant Stock which are at any time issuable hereunder, so long as any shares
of Common Stock shall be so listed. The Issuer will also so list on each
securities exchange or market, and will maintain such listing of, any other
securities which the Holder of this Warrant shall be entitled to receive upon
the exercise of this Warrant if at the time any securities of the same class
shall be listed on such securities exchange or market by the Issuer.

               (c) Covenants. The Issuer shall not by any action including,
without limitation, amending the Certificate of Incorporation or the by-laws of
the Issuer, or through any reorganization, transfer of assets, consolidation,
merger, dissolution, issue or sale of securities or any other action, avoid or
seek to avoid the observance or performance of any of the terms of this Warrant,
but will at all times in good faith assist in the carrying out of all such terms
and in the taking of all such actions as may be necessary or appropriate to
protect the rights of the Holder hereof against dilution (to the extent
specifically provided herein) or impairment. Without limiting the generality of
the foregoing, the Issuer will (i) not permit the par value, if any, of its
Common Stock to exceed the then effective Warrant Price, (ii) not amend or
modify any provision of the Certificate of Incorporation or by-laws of the
Issuer in any manner that would adversely affect in any way the powers,
preferences or relative participating, optional or other special rights of the
Common Stock or which would adversely affect the rights of the Holders of the
Warrants, (iii) take all such action as may be reasonably necessary in order
that the Issuer may validly and legally issue fully paid and nonassessable
shares of Common Stock, free and



                                      -4-
<PAGE>   5
clear of any liens, claims, encumbrances and restrictions (other than as
provided herein) upon the exercise of this Warrant, and (iv) use its best
efforts to obtain all such authorizations, exemptions or consents from any
public regulatory body having jurisdiction thereof as may be reasonably
necessary to enable the Issuer to perform its obligations under this Warrant.

               (d) Loss, Theft, Destruction of Warrants. Upon receipt of
evidence satisfactory to the Issuer of the ownership of and the loss, theft,
destruction or mutilation of any Warrant and, in the case of any such loss,
theft or destruction, upon receipt of indemnity or security satisfactory to the
Issuer or, in the case of any such mutilation, upon surrender and cancellation
of such Warrant, the Issuer will make and deliver, in lieu of such lost, stolen,
destroyed or mutilated Warrant, a new Warrant of like tenor and representing the
right to purchase the same number of shares of Common Stock.

               (e) Rights and Obligations under the Registration Rights
Agreement. The shares of Warrant Stock are entitled to the benefits and subject
to the terms of the Registration Rights Agreement dated as of even date herewith
between the Issuer and the Holders listed on the signature pages thereof (as
amended from time to time, the "Registration Rights Agreement"). The Issuer
shall keep or cause to be kept a copy of the Registration Rights Agreement, and
any amendments thereto, at its chief executive office and shall furnish, without
charge, copies thereof to the Holder upon request.

               4. Adjustment of Warrant Price and Warrant Share Number. The
number and kind of Securities purchasable upon the exercise of this Warrant and
the Warrant Price shall be subject to adjustment from time to time upon the
happening of certain events as follows:

               (a) Recapitalization, Reorganization, Reclassification,
Consolidation, Merger or Sale.

                   (i) In case the Issuer after the Original Issue Date shall do
               any of the following (each, a "Triggering Event"): (a)
               consolidate with or merge into any other Person and the Issuer
               shall not be the continuing or surviving corporation of such
               consolidation or merger, or (b) permit any other Person to
               consolidate with or merge into the Issuer and the Issuer shall be
               the continuing or surviving Person but, in connection with such
               consolidation or merger, any Capital Stock of the Issuer shall be
               changed into or exchanged for Securities of any other Person or
               cash or any other property, or (c) transfer all or substantially
               all of its properties or assets to any other Person, or (d)
               effect a capital reorganization or reclassification of its
               Capital Stock, then, and in the case of each such Triggering
               Event, proper provision shall be made so that, upon the basis and
               the terms and in the manner provided in this Warrant, the Holder
               of this Warrant shall be entitled (x) upon the exercise hereof at
               any time after the consummation of such Triggering Event, to the
               extent this Warrant is not exercised prior to such Triggering
               Event, to receive at the Warrant Price in effect at the time
               immediately prior to the consummation of such Triggering Event in
               lieu of the Common Stock issuable upon such exercise of this
               Warrant prior to such Triggering Event, the Securities, cash and
               property to which such Holder would have been entitled upon the
               consummation of such Triggering Event if such Holder had
               exercised the rights represented by this Warrant immediately
               prior thereto, subject to adjustments (subsequent to such
               corporate action) as nearly equivalent as possible to the
               adjustments provided for in Section 4 hereof or (y) to sell this
               Warrant



                                      -5-
<PAGE>   6
               (or, at such Holder's election, a portion hereof) concurrently
               with the Triggering Event to the Person continuing after or
               surviving such Triggering Event, or to the Issuer (if Issuer is
               the continuing or surviving Person) at a sales price equal to the
               amount of cash, property and/or Securities to which a holder of
               the number of shares of Common Stock which would otherwise have
               been delivered upon the exercise of this Warrant would have been
               entitled upon the effective date or closing of any such
               Triggering Event (the "Event Consideration"), less the amount or
               portion of such Event Consideration having a fair value equal to
               the aggregate Warrant Price applicable to this Warrant or the
               portion hereof so sold.

                   (ii) Notwithstanding anything contained in this Warrant to
               the contrary, the Issuer will not effect any Triggering Event
               unless, prior to the consummation thereof, each Person (other
               than the Issuer) which may be required to deliver any Securities,
               cash or property upon the exercise of this Warrant as provided
               herein shall assume, by written instrument delivered to, and
               reasonably satisfactory to, the Holder of this Warrant, (A) the
               obligations of the Issuer under this Warrant (and if the Issuer
               shall survive the consummation of such Triggering Event, such
               assumption shall be in addition to, and shall not release the
               Issuer from, any continuing obligations of the Issuer under this
               Warrant) and (B) the obligation to deliver to such Holder such
               shares of Securities, cash or property as, in accordance with the
               foregoing provisions of this subsection (a), such Holder shall be
               entitled to receive, and such Person shall have similarly
               delivered to such Holder an opinion of counsel for such Person,
               which counsel shall be reasonably satisfactory to such Holder,
               stating that this Warrant shall thereafter continue in full force
               and effect and the terms hereof (including, without limitation,
               all of the provisions of this subsection (a)) shall be applicable
               to the Securities, cash or property which such Person may be
               required to deliver upon any exercise of this Warrant or the
               exercise of any rights pursuant hereto.

                   (iii) If with respect to any Triggering Event, the Holder of
               this Warrant has exercised its right as provided in clause (y) of
               subparagraph (i) of this subsection (a) to sell this Warrant or a
               portion thereof, the Issuer agrees that as a condition to the
               consummation of any such Triggering Event the Issuer shall secure
               such right of Holder to sell this Warrant to the Person
               continuing after or surviving such Triggering Event and the
               Issuer shall not effect any such Triggering Event unless upon or
               prior to the consummation thereof the amounts of cash, property
               and/or Securities required under such clause (y) are delivered to
               the Holder of this Warrant. The obligation of the Issuer to
               secure such right of the Holder to sell this Warrant shall be
               subject to such Holder's cooperation with the Issuer, including,
               without limitation, the giving of customary representations and
               warranties to the purchaser in connection with any such sale.
               Prior notice of any Triggering Event shall be given to the Holder
               of this Warrant in accordance with Section 13 hereof.

               (b) Subdivision or Combination of Shares. If the Issuer, at any
time while this Warrant is outstanding, shall subdivide or combine any shares of
Common Stock, (i) in case of subdivision of shares, the Warrant Price shall be
proportionately reduced (as at the effective date of such subdivision or, if the
Issuer shall take a record of Holders of its Common Stock for the purpose of so
subdividing, as at the applicable record date, whichever is earlier) to reflect
the



                                      -6-
<PAGE>   7
increase in the total number of shares of Common Stock outstanding as a result
of such subdivision, or (ii) in the case of a combination of shares, the Warrant
Price shall be proportionately increased (as at the effective date of such
combination or, if the Issuer shall take a record of Holders of its Common Stock
for the purpose of so combining, as at the applicable record date, whichever is
earlier) to reflect the reduction in the total number of shares of Common Stock
outstanding as a result of such combination.

               (c) Certain Dividends and Distributions. If the Issuer, at any
time while this Warrant is outstanding, shall:

                   (i) Stock Dividends. Pay a dividend in, or make any other
               distribution to its stockholders (without consideration therefor)
               of, shares of Common Stock, the Warrant Price shall be adjusted,
               as at the date the Issuer shall take a record of the Holders of
               the Issuer's Capital Stock for the purpose of receiving such
               dividend or other distribution (or if no such record is taken, as
               at the date of such payment or other distribution), to that price
               determined by multiplying the Warrant Price in effect immediately
               prior to such record date (or if no such record is taken, then
               immediately prior to such payment or other distribution), by a
               fraction (1) the numerator of which shall be the total number of
               shares of Common Stock outstanding immediately prior to such
               dividend or distribution, and (2) the denominator of which shall
               be the total number of shares of Common Stock outstanding
               immediately after such dividend or distribution (plus in the
               event that the Issuer paid cash for fractional shares, the number
               of additional shares which would have been outstanding had the
               Issuer issued fractional shares in connection with said
               dividends); or

                   (ii) Other Dividends. Pay a dividend on, or make any
               distribution of its assets upon or with respect to (including,
               but not limited to, a distribution of its property as a dividend
               in liquidation or partial liquidation or by way of return of
               capital), the Common Stock (other than as described in clause (i)
               of this subsection (c)), or in the event that the Issuer shall
               offer options or rights to subscribe for shares of Common Stock,
               or issue any Common Stock Equivalents, to all of its holders of
               Common Stock, then on the record date for such payment,
               distribution or offer or, in the absence of a record date, on the
               date of such payment, distribution or offer, the Holder shall
               receive what the Holder would have received had it exercised this
               Warrant in full immediately prior to the record date of such
               payment, distribution or offer or, in the absence of a record
               date, immediately prior to the date of such payment, distribution
               or offer.

               (d) Issuance of Additional Shares of Common Stock. If the Issuer,
at any time while this Warrant is outstanding, shall issue any Additional Shares
of Common Stock (otherwise than as provided in the foregoing subsections (a)
through (c) of this Section 4), at a price per share less than the Warrant Price
then in effect or without consideration, then the Warrant Price upon each such
issuance shall be adjusted to that price (rounded to the nearest cent)
determined by multiplying the Warrant Price then in effect by a fraction:

                   (i) the numerator of which shall be equal to the sum of (A)
               the number of shares of Common Stock outstanding immediately
               prior to the issuance of such Additional Shares of Common Stock
               plus (B) the number of shares of Common Stock



                                      -7-
<PAGE>   8
               (rounded to the nearest whole share) which the aggregate
               consideration for the total number of such Additional Shares of
               Common Stock so issued would purchase at a price per share equal
               to the greater of the Per Share Market Value and the Warrant
               Price then in effect, and

                   (ii) the denominator of which shall be equal to the number of
               shares of Common Stock outstanding immediately after the issuance
               of such Additional Shares of Common Stock.

The provisions of this subsection (d) shall not apply under any of the
circumstances for which an adjustment is provided in subsections (a), (b) or (c)
of this Section 4. No adjustment of the Warrant Price shall be made under this
subsection (d) upon the issuance of any Additional Shares of Common Stock which
are issued pursuant to any Common Stock Equivalent if upon the issuance of such
Common Stock Equivalent (x) any adjustment shall have been made pursuant to
subsection (e) of this Section 4 or (Y) no adjustment was required pursuant to
subsection (e) of this Section 4. No adjustment of the Warrant Price shall be
made under this subsection (d) in an amount less than $.01 per share, but any
such lesser adjustment shall be carried forward and shall be made at the time
and together with the next subsequent adjustment, if any, which together with
any adjustments so carried forward shall amount to $.01 per share or more,
provided that upon any adjustment of the Warrant Price as a result of any
dividend or distribution payable in Common Stock or Convertible Securities or
the reclassification, subdivision or combination of Common Stock into a greater
or smaller number of shares, the foregoing figure of $.01 per share (or such
figure as last adjusted) shall be adjusted (to the nearest one-half cent) in
proportion to the adjustment in the Warrant Price.

               (e) Issuance of Common Stock Equivalents. If the Issuer, at any
time while this Warrant is outstanding, shall issue any Common Stock Equivalent
and the price per share for which Additional Shares of Common Stock may be
issuable thereafter pursuant to such Common Stock Equivalent shall be less than
the Warrant Price then in effect, or if, after any such issuance of Common Stock
Equivalents, the price per share for which Additional Shares of Common Stock may
be issuable thereafter is amended or adjusted, and such price as so amended
shall be less than the Warrant Price, then the Warrant Price upon each such
issuance or amendment shall be adjusted as provided in the first sentence of
subsection (d) of this Section 4 on the basis that (1) the maximum number of
Additional Shares of Common Stock issuable pursuant to all such Common Stock
Equivalents shall be deemed to have been issued (whether or not such Common
Stock Equivalents are actually then exercisable, convertible or exchangeable in
whole or in part) as of the earlier of (A) the date on which the Issuer shall
enter into a firm contract for the issuance of such Common Stock Equivalent, or
(B) the date of actual issuance of such Common Stock Equivalent, and (2) the
aggregate consideration for such maximum number of Additional Shares of Common
Stock shall be deemed to be the minimum consideration received or receivable by
the Issuer for the issuance of such Additional Shares of Common Stock pursuant
to such Common Stock Equivalent. No adjustment of the Warrant Price shall be
made under this subsection (e) upon the issuance of any Convertible Security
which is issued pursuant to the exercise of any warrants or other subscription
or purchase rights therefor, if any adjustment shall previously have been made
in the Warrant Price then in effect upon the issuance of such warrants or other
rights pursuant to this subsection (e).



                                      -8-
<PAGE>   9
               (f) Purchase of Common Stock by the Issuer. If the Issuer at any
time while this Warrant is outstanding shall, directly or indirectly through a
Subsidiary or otherwise, purchase, redeem or otherwise acquire any shares of
Common Stock at a price per share greater than the Per Share Market Value, then
the Warrant Price upon each such purchase, redemption or acquisition shall be
adjusted to that price determined by multiplying such Warrant Price by a
fraction (i) the numerator of which shall be the number of shares of Common
Stock outstanding immediately prior to such purchase, redemption or acquisition
minus the number of shares of Common Stock which the aggregate consideration for
the total number of such shares of Common Stock so purchased, redeemed or
acquired would purchase at the Per Share Market Value; and (ii) the denominator
of which shall be the number of shares of Common Stock outstanding immediately
after such purchase, redemption or acquisition. For the purposes of this
subsection (f), the date as of which the Per Share Market Price shall be
computed shall be the earlier of (x) the date on which the Issuer shall enter
into a firm contract for the purchase, redemption or acquisition of such Common
Stock, or (y) the date of actual purchase, redemption or acquisition of such
Common Stock. For the purposes of this subsection (f), a purchase, redemption or
acquisition of a Common Stock Equivalent shall be deemed to be a purchase of the
underlying Common Stock, and the computation herein required shall be made on
the basis of the full exercise, conversion or exchange of such Common Stock
Equivalent on the date as of which such computation is required hereby to be
made, whether or not such Common Stock Equivalent is actually exercisable,
convertible or exchangeable on such date.

               (g) Other Provisions Applicable to Adjustments Under this Section
4. The following provisions shall be applicable to the making of adjustments in
the Warrant Price hereinbefore provided in Section 4:

                   (i) Computation of Consideration. The consideration received
               by the Issuer shall be deemed to be the following: to the extent
               that any Additional Shares of Common Stock or any Common Stock
               Equivalents shall be issued for a cash consideration, the
               consideration received by the Issuer therefor, or if such
               Additional Shares of Common Stock or Common Stock Equivalents are
               offered by the Issuer for subscription, the subscription price,
               or, if such Additional Shares of Common Stock or Common Stock
               Equivalents are sold to underwriters or dealers for public
               offering without a subscription offering, the public offering
               price, in any such case excluding any amounts paid or receivable
               for accrued interest or accrued dividends and without deduction
               of any compensation, discounts, commissions, or expenses paid or
               incurred by the Issuer for or in connection with the underwriting
               thereof or otherwise in connection with the issue thereof; to the
               extent that such issuance shall be for a consideration other than
               cash, then, except as herein otherwise expressly provided, the
               fair market value of such consideration at the, time of such
               issuance as determined in good faith by the Board. The
               consideration for any Additional Shares of Common Stock issuable
               pursuant to any Common Stock Equivalents shall be the
               consideration received by the Issuer for issuing such Common
               Stock Equivalents, plus the additional consideration payable to
               the Issuer upon the exercise, conversion or exchange of such
               Common Stock Equivalents. In case of the issuance at any time of
               any Additional Shares of Common Stock or Common Stock Equivalents
               in payment or satisfaction of any dividend upon any class of
               Capital Stock of the Issuer other than Common Stock, the Issuer
               shall be deemed to have received for such Additional Shares of
               Common Stock or Common Stock Equivalents a



                                      -9-
<PAGE>   10
               consideration equal to the amount of such dividend so paid or
               satisfied. In any case in which the consideration to be received
               or paid shall be other than cash, the Board shall notify the
               Holder of this Warrant of its determination of the fair market
               value of such consideration prior to payment or accepting receipt
               thereof. If, within 30 days after receipt of said notice, the
               Majority Holders shall notify the Board in writing of their
               objection to such determination, a determination of the fair
               market value of such consideration shall be made by an
               Independent Appraiser selected by the Majority Holders with the
               approval of the Board (which approval shall not be unreasonably
               withheld), whose fees and expenses shall be paid by the Issuer.

                   (ii) Readjustment of Warrant Price. Upon the expiration or
               termination of the right to convert, exchange or exercise any
               Common Stock Equivalent the issuance of which effected an
               adjustment in the Warrant Price, if such Common Stock Equivalent
               shall not have been converted, exercised or exchanged in its
               entirety, the number of shares of Common Stock deemed to be
               issued and outstanding by reason of the fact that they were
               issuable upon conversion, exchange or exercise of any such Common
               Stock Equivalent shall no longer be computed as set forth above,
               and the Warrant Price shall forthwith be readjusted and
               thereafter be the price which it would have been (but reflecting
               any other adjustments in the Warrant Price made pursuant to the
               provisions of this Section 4 after the issuance of such Common
               Stock Equivalent) had the adjustment of the Warrant Price been
               made in accordance with the issuance or sale of the number of
               Additional Shares of Common Stock actually issued upon
               conversion, exchange or issuance of such Common Stock Equivalent
               and thereupon only the number of Additional Shares of Common
               Stock actually so issued shall be deemed to have been issued and
               only the consideration actually received by the Issuer (computed
               as in clause (i) of this subsection (g)) shall be deemed to have
               been received by the Issuer.

                   (iii) Outstanding Common Stock. The number of shares of
               Common Stock at any time outstanding shall (A) not include any
               shares thereof then directly or indirectly owned or held by or
               for the account of the Issuer or any of its Subsidiaries, and (B)
               be deemed to include all shares of Common Stock then issuable
               upon conversion, exercise or exchange of any then outstanding
               Common Stock Equivalents or any other evidences of Indebtedness,
               shares of Capital Stock or other Securities which are or may be
               at any time convertible into or exchangeable for shares of Common
               Stock or Other Common Stock.

               (h) Other Action Affecting Common Stock. In case after the
Original Issue Date the Issuer shall take any action affecting its Common Stock,
other than an action described in any of the foregoing subsections (a) through
(g) of this Section 4, inclusive, and the failure to make any adjustment would
not fairly protect the purchase rights represented by this Warrant in accordance
with the essential intent and principle of this Section 4, then the Warrant
Price shall be adjusted in such manner and at such time as the Board may in good
faith determine to be equitable in the circumstances.

               (i) Adjustment of Warrant Share Number. Upon each adjustment in
the Warrant Price pursuant to any of the foregoing provisions of this Section 4,
the Warrant Share Number shall be adjusted, to the nearest one hundredth (100th)
of a whole share, to the product obtained



                                      -10-
<PAGE>   11
by multiplying the Warrant Share Number immediately prior to such adjustment in
the Warrant Price by a fraction, the numerator of which shall be the Warrant
Price immediately before giving effect to such adjustment and the denominator of
which shall be the Warrant Price immediately after giving effect to such
adjustment. If the Issuer shall be in default under any provision contained in
Section 3 of this Warrant so that shares issued at the Warrant Price adjusted in
accordance with this Section 4 would not be validly issued, the adjustment of
the Warrant Share Number provided for in the foregoing sentence shall
nonetheless be made and the Holder of this Warrant shall be entitled to purchase
such greater number of shares at the lowest price at which such shares may then
be validly issued under applicable law. Such exercise shall not constitute a
waiver of any claim arising against the Issuer by reason of its default under
Section 3 of this Warrant.

               (j) Form of Warrant after Adjustments. The form of this Warrant
need not be changed because of any adjustments in the Warrant Price or the
number and kind of Securities purchasable upon the exercise of this Warrant.

               5. Notice of Adjustments. Whenever the Warrant Price or Warrant
Share Number shall be adjusted pursuant to Section 4 hereof (for purposes of
this Section 5, each an "adjustment"), the Issuer shall cause its Chief
Financial Officer to prepare and execute a certificate setting forth, in
reasonable detail, the event requiring the adjustment, the amount of the
adjustment, the method by which such adjustment was calculated (including a
description of the basis on which the Board made any determination hereunder),
and the Warrant Price and Warrant Share Number after giving effect to such
adjustment, and shall cause copies of such certificate to be delivered to the
Holder of this Warrant promptly after each adjustment. Any dispute between the
Issuer and the Holder of this Warrant with respect to the matters set forth in
such certificate may at the option of the Holder of this Warrant be submitted to
one of the national accounting firms currently known as the "big five" selected
by the Holder, provided that the Issuer shall have 10 days after receipt of
notice from such Holder of its selection of such firm to object thereto, in
which case such Holder shall select another such firm and the Issuer shall have
no such right of objection. The firm selected by the Holder of this Warrant as
provided in the preceding sentence shall be instructed to deliver a written
opinion as to such matters to the Issuer and such Holder within 30 days after
submission to it of such dispute. Such opinion shall be final and binding on the
parties hereto. The fees and expenses of such accounting firm shall be paid by
the Issuer.

               6. Fractional Shares. No fractional shares of Warrant Stock will
be issued in connection with and exercise hereof, but in lieu of such fractional
shares, the Issuer shall make a cash payment therefor equal in amount to the
product of the applicable fraction multiplied by the Per Share Market Value then
in effect.

               7. [Intentionally Omitted.] [Call.(1) Notwithstanding anything
herein to the contrary, the Issuer, at its option, may call up to (i) 50% of
this Warrant if the Per Share Market Value of the Common Stock has been equal to
or greater than 200% of the Warrant Price for a period of 20 consecutive Trading
Days immediately prior to the date of delivery of the Call Notice (a "Call


-----------------------
(1) Each Purchaser shall receive two warrant certificates, one of which shall
contain this language.


                                      -11-
<PAGE>   12
Notice Period") and (ii) up to 50% of this Warrant if the Per Share Market Value
of the Common Stock has been equal to or greater than 250% of the Warrant Price
during a Call Notice Period by providing the Holder of this Warrant written
notice pursuant to Section 13 (the "Call Notice") at any time or from time to
time after: (A) the Common Stock has a trading volume on the OTC Bulletin Board
(or on such other United States stock exchange or public trading market the
Common Stock is then traded on) of at least 150,000 shares of Common Stock per
day on each of the days of the Call Notice Period; and (B) the Registration
Statement has been declared effective and has been effective, without lapse or
suspension of any kind, for a period of 60 consecutive calendar days; provided,
however, the Registration Statement must be effective from the date of delivery
of the Call Notice until the date which is the later of (i) the date the Holder
exercises the Warrant pursuant to the Call Notice and (ii) the 20th day after
the Holder receives the Call Notice (the "Early Termination Date"); provided,
further, that the Issuer may not provide Call Notice(s) for more than 20% of
this Warrant during any 30 day period. The rights and privileges granted
pursuant to this Warrant with respect to the shares of Warrant Stock subject to
the Call Notice (the "Called Warrant Shares") shall expire on the Early
Termination Date if this Warrant is not exercised with respect to such Called
Warrant Shares prior to such Early Termination Date. In the event this Warrant
is not exercised with respect to the Called Warrant Shares, the Issuer shall
remit to the Holder of this Warrant (i) $.001 per Called Warrant Share and (ii)
a new Warrant representing the number of shares of Warrant Stock, if any, which
shall not have been subject to the Call Notice upon the Holder tendering to the
Issuer the applicable Warrant certificate.

               8. Warrant Exercise Restriction. Notwithstanding anything to the
contrary set forth in this Warrant, at no time may a holder of this Warrant
exercise this Warrant, or a portion hereof, if the number of shares of Common
Stock to be issued pursuant to such exercise would exceed, when aggregated with
all other shares of Common Stock owned by such holder at such time, would result
in such holder owning more than 9.99% of all of the Common Stock issued and
outstanding at such time; provided, however, that upon a holder of this Warrant
providing the Issuer with 75 days notice (pursuant to Section 13 hereof) (the
"Waiver Notice") that such holder would like to waive Section 8 of this Warrant
with regard to any or all shares of Common Stock issuable upon exercise of the
Warrant, this Section 8 will be of no force or effect with regard to the number
of shares exercisable pursuant to the Warrant, or the applicable portion
thereof, referenced in the Waiver Notice.

               9. Definitions. For the purposes of this Warrant, the following
terms have the following meanings:

                  "Additional Shares of Common Stock" means all shares of Common
               Stock issued by the Issuer after the Original Issue Date, and all
               shares of Other Common, if any, issued by the Issuer after the
               Original Issue Date, except (i) the Conversion Shares, (ii) the
               Warrant Stock, (iii) any shares of Common Stock issued pursuant
               to the exercise of stock options issued by the Issuer to its
               employees pursuant to duly approved Issuer stock option plans,
               and (iv) any shares of Common Stock issued by the Issuer as
               dividends pursuant to the certificate of designation relating to
               the Issuer's Series A Convertible Preferred Stock, par value
               $.001 per share.

               "Board" shall mean the Board of Directors of the Issuer.



                                      -12-
<PAGE>   13
               "Capital Stock" means and includes (i) any and all shares,
interests, participations or other equivalents of or interests in (however
designated) corporate stock, including, without limitation, shares of preferred
or preference stock, (ii) all partnership interests (whether general or limited)
in any Person which is a partnership, (iii) all membership interests or limited
liability company interests in any limited liability company, and (iv) all
equity or ownership interests in any Person of any other type.

               "Certificate of Incorporation" means the Certificate of
Incorporation of the Issuer as in effect on the Original Issue Date, and as
hereafter from time to time amended, modified, supplemented or restated in
accordance with the terms hereof and thereof and pursuant to applicable law.

               "Common Stock" means the Common Stock, par value $.001 per share,
of the Issuer and any other Capital Stock into which such stock may hereafter be
changed.

               "Common Stock Equivalent" means any Convertible Security or
warrant, option or other right to subscribe for or purchase any Additional
Shares of Common Stock or any Convertible Security.

               "Convertible Securities" means evidences of Indebtedness, shares
of Capital Stock or other Securities which are or may be at any time convertible
into or exchangeable for Additional Shares of Common Stock. The term
"Convertible Security" means one of the Convertible Securities.

               "Governmental Authority" means any governmental, regulatory or
self-regulatory entity, department, body, official, authority, commission,
board, agency or instrumentality, whether federal, state or local, and whether
domestic or foreign.

               "Holders" mean the Persons who shall from time to time own any
Warrant. The term "Holder" means one of the Holders.

               "Independent Appraiser" means a nationally recognized or major
regional investment banking firm or firm of independent certified public
accountants of recognized standing (which may be the firm that regularly
examines the financial statements of the Issuer) that is regularly engaged in
the business of appraising the Capital Stock or assets of corporations or other
entities as going concerns, and which is not affiliated with either the Issuer
or the Holder of any Warrant.

               "Issuer" means GreyStone Digital Technology, Inc., a Delaware
corporation, and its successors.

               "Majority Holders" means at any time the Holders of Warrants
exercisable for a majority of the shares of Warrant Stock issuable under the
Warrants at the time outstanding.

               "Original Issue Date" means May __, 2000.



                                      -13-
<PAGE>   14
               "Other Common" means any other Capital Stock of the Issuer of any
class which shall be authorized at any time after the date of this Warrant
(other than Common Stock) and which shall have the right to participate in the
distribution of earnings and assets of the Issuer without limitation as to
amount.

               "OTC Bulletin Board" means the over-the-counter electronic
bulletin board.

               "Person" means an individual, corporation, limited liability
company, partnership, joint stock company, trust, unincorporated organization,
joint venture, Governmental Authority or other entity of whatever nature.

               "Per Share Market Value" means on any particular date (a) the
closing bid price per share of the Common Stock on such date on the OTC Bulletin
Board or other registered national stock exchange on which the Common Stock is
then listed or if there is no such price on such date, then the closing bid
price on such exchange or quotation system on the date nearest preceding such
date, or (b) if the Common Stock is not listed then on the OTC Bulletin Board or
any registered national stock exchange, the closing bid price for a share of
Common Stock in the over-the-counter market, as reported by the OTC Bulletin
Board or in the National Quotation Bureau Incorporated or similar organization
or agency succeeding to its functions of reporting prices) at the close of
business on such date, or (c) if the Common Stock is not then reported by the
OTC Bulletin Board or the National Quotation Bureau Incorporated (or similar
organization or agency succeeding to its functions of reporting prices), then
the average of the "Pink Sheet" quotes for the relevant conversion period, as
determined in good faith by the holder, or (d) if the Common Stock is not then
publicly traded the fair market value of a share of Common Stock as determined
by an Independent Appraiser selected in good faith by the Majority Holders;
provided, however, that the Issuer, after receipt of the determination by such
Independent Appraiser, shall have the right to select an additional Independent
Appraiser, in which case, the fair market value shall be equal to the average of
the determinations by each such Independent Appraiser; and provided, further
that all determinations of the Per Share Market Value shall be appropriately
adjusted for any stock dividends, stock splits or other similar transactions
during such period. The determination of fair market value by an Independent
Appraiser shall be based upon the fair market value of the Issuer determined on
a going concern basis as between a willing buyer and a willing seller and taking
into account all relevant factors determinative of value, and shall be final and
binding on all parties. In determining the fair market value of any shares of
Common Stock, no consideration shall be given to any restrictions on transfer of
the Common Stock imposed by agreement or by federal or state securities laws, or
to the existence or absence of, or any limitations on, voting rights.

               "Purchase Agreement" means the Series A Convertible Preferred
Stock Purchase Agreement dated as of May __, 2000 among the Issuer and the
investors a party thereto.

               "Registration Rights Agreement" has the meaning specified in
Section 3(e) hereof.



                                      -14-
<PAGE>   15
               "Securities" means any debt or equity securities of the Issuer,
whether now or hereafter authorized, any instrument convertible into or
exchangeable for Securities or a Security, and any option, warrant or other
right to purchase or acquire any Security. "Security" means one of the
Securities.

               "Securities Act" means the Securities Act of 1933, as amended, or
any similar federal statute then in effect.

               "Subsidiary" means any corporation at least 50% of whose
outstanding Voting Stock shall at the time be owned directly or indirectly by
the Issuer or by one or more of its Subsidiaries, or by the Issuer and one or
more of its Subsidiaries.

               "Trading Day" means (a) a day on which the Common Stock is traded
on the over the counter market as reported by the OTC Bulletin Board, or (b) if
the Common Stock is not listed on the OTC Bulletin Board, a day on which the
Common Stock is traded on any other registered national stock exchange, or (c)
if the Common Stock is not quoted on the OTC Bulletin Board, a day on which the
Common Stock is quoted in the over-the-counter market as reported by the
National Quotation Bureau Incorporated (or any similar organization or agency
succeeding its functions of reporting prices); provided, however, that in the
event that the Common Stock is not listed or quoted as set forth in (a), (b) and
(c) hereof, then Trading Day shall mean any day except Saturday, Sunday and any
day which shall be a legal holiday or a day on which banking institutions in the
State of New York are authorized or required by law or other government action
to close.

               "Term" has the meaning specified in Section 1 hereof.

               "Voting Stock", as applied to the Capital Stock of any
corporation, means Capital Stock of any class or classes (however designated)
having ordinary voting power for the election of a majority of the members of
the Board of Directors (or other governing body) of such corporation, other than
Capital Stock having such power only by reason of the happening of a
contingency.

               "Warrants" means the Warrants issued and sold pursuant to the
Purchase Agreement, including, without limitation, this Warrant, and any other
warrants of like tenor issued in substitution or exchange for any thereof
pursuant to the provisions of Section 2(c), 2(d) or 2(e) hereof or of any of
such other Warrants.

               "Warrant Price" means $[____], as such price may be adjusted from
time to time as shall result from the adjustments specified in this Warrant,
including Section 4 hereto.

               "Warrant Share Number" means at any time the aggregate number of
shares of Warrant Stock which may at such time be purchased upon exercise of
this Warrant, after giving effect to all prior adjustments and increases to such
number made or required to be made under the terms hereof.



                                      -15-
<PAGE>   16
               "Warrant Stock" means Common Stock issuable upon exercise of any
Warrant or Warrants or otherwise issuable pursuant to any Warrant or Warrants.

10. Other Notices.  In case at any time:

                   (A) the Issuer shall make any distributions to the holders of
                       Common Stock; or

                   (B) the Issuer shall authorize the granting to all holders of
                       its Common Stock of rights to subscribe for or purchase
                       any shares of Capital Stock of any class or of any Common
                       Stock Equivalents or Convertible Securities or other
                       rights; or

                   (C) there shall be any reclassification of the Capital Stock
                       of the Issuer; or

                   (D) there shall be any capital reorganization by the Issuer;
                       or

                   (E) there shall be any (i) consolidation or merger involving
                       the Issuer or (ii) sale, transfer or other disposition of
                       all or substantially all of the Issuer's property, assets
                       or business (except a merger or other reorganization in
                       which the Issuer shall be the surviving corporation and
                       its shares of Capital Stock shall continue to be
                       outstanding and unchanged and except a consolidation,
                       merger, sale, transfer or other disposition involving a
                       wholly-owned Subsidiary); or

                   (F) there shall be a voluntary or involuntary dissolution,
                       liquidation or winding-up of the Issuer or any partial
                       liquidation of the Issuer or distribution to holders of
                       Common Stock;

then, in each of such cases, the Issuer shall give written notice to the Holder
of the date on which (i) the books of the Issuer shall close or a record shall
be taken for such dividend, distribution or subscription rights or (ii) such
reorganization, reclassification, consolidation, merger, disposition,
dissolution, liquidation or winding-up, as the case may be, shall take place.
Such notice also shall specify the date as of which the holders of Common Stock
of record shall participate in such dividend, distribution or subscription
rights, or shall be entitled to exchange their certificates for Common Stock for
securities or other property deliverable upon such reorganization,
reclassification, consolidation, merger, disposition, dissolution, liquidation
or winding-up, as the case may be. Such notice shall be given at least 20 days
prior to the action in question and not less than 20 days prior to the record
date or the date on which the Issuer's transfer books are closed in respect
thereto. The Issuer shall give to the Holder notice of all meetings and actions
by written consent of its stockholders, at the same time in the same manner as
notice of any meetings of stockholders is required to be given to stockholders
who do not waive such notice (or, if such requires no notice, then 2 Trading
Days written notice thereof



                                      -16-
<PAGE>   17
describing the matters upon which action is to be taken). The Holder shall have
the right to send two (2) representatives selected by it to each meeting, who
shall be permitted to attend, but not vote at, such meeting and any adjournments
thereof. This Warrant entitles the Holder to receive copies of all financial and
other information distributed or required to be distributed to the holders of
the Common Stock.

               11. Amendment and Waiver. Any term, covenant, agreement or
condition in this Warrant may be amended, or compliance therewith may be waived
(either generally or in a particular instance and either retroactively or
prospectively), by a written instrument or written instruments executed by the
Issuer and the Majority Holders; provided, however, that no such amendment or
waiver shall reduce the Warrant Share Number, increase the Warrant Price,
shorten the period during which this Warrant may be exercised or modify any
provision of this Section 9 without the consent of the Holder of this Warrant.

               12. Governing Law. THIS WARRANT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT GIVING
EFFECT TO PRINCIPLES OF CONFLICTS OF LAW.

               13. Notices. Any and all notices or other communications or
deliveries required or permitted to be provided hereunder shall be in writing
and shall be deemed given and effective on the earlier of (i) the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile telephone number specified for notice prior to 5:00 p.m., eastern
time, on a Business Day, (ii) the Business Day after the date of transmission,
if such notice or communication is delivered via facsimile at the facsimile
telephone number specified for notice later than 5:00 p.m., eastern time, on any
date and earlier than 11:59 p.m., eastern time, on such date, (iii) the Business
Day following the date of mailing, if sent by nationally recognized overnight
courier service or (iv) actual receipt by the party to whom such notice is
required to be given. The addresses for such communications shall be with
respect to the Holder of this Warrant or of Warrant Stock issued pursuant
hereto, addressed to such Holder at its last known address or facsimile number
appearing on the books of the Issuer maintained for such purposes, or with
respect to the Issuer, addressed to:

        GreyStone Digital Technology, Inc.
        4950 Murphy Canyon Road
        San Diego, CA  92123
        Attention: Carolyn Harris, Esq.
        Tel No.: (858) 874-7000
        Fax No.: (858) 874-7019

or to such other address or addresses or facsimile number or numbers as any such
party may most recently have designated in writing to the other parties hereto
by such notice. Copies of notices to the Holders shall be sent to Parker Chapin
LLP, The Chrysler Building, 405 Lexington Avenue, New York, New York 10174,
Attention: Christopher S. Auguste, Esq., facsimile no.: (212) 704-6288. Copies
of notices to the Issuer shall be sent to Resch Polster Alpert & Berger LLP,
10390 Santa Monica Boulevard, 4th Floor, Los Angeles, California 90025,
Attention: Aaron A. Grunfeld, Esq., facsimile no.: (310) 552-3209.



                                      -17-
<PAGE>   18
               14. Warrant Agent. The Issuer may, by written notice to each
Holder of this Warrant, appoint an agent having an office in New York, New York
for the purpose of issuing shares of Warrant Stock on the exercise of this
Warrant pursuant to subsection (b) of Section 2 hereof, exchanging this Warrant
pursuant to subsection (d) of Section 2 hereof or replacing this Warrant
pursuant to subsection (d) of Section 3 hereof, or any of the foregoing, and
thereafter any such issuance, exchange or replacement, as the case may be, shall
be made at such office by such agent.

               15. Remedies. The Issuer stipulates that the remedies at law of
the Holder of this Warrant in the event of any default or threatened default by
the Issuer in the performance of or compliance with any of the terms of this
Warrant are not and will not be adequate and that, to the fullest extent
permitted by law, such terms may be specifically enforced by a decree for the
specific performance of any agreement contained herein or by an injunction
against a violation of any of the terms hereof or otherwise.

               16. Successors and Assigns. This Warrant and the rights evidenced
hereby shall inure to the benefit of and be binding upon the successors and
assigns of the Issuer, the Holder hereof and (to the extent provided herein) the
Holders of Warrant Stock issued pursuant hereto, and shall be enforceable by any
such Holder or Holder of Warrant Stock

               17. Modification and Severability. If, in any action before any
court or agency legally empowered to enforce any provision contained herein, any
provision hereof is found to be unenforceable, then such provision shall be
deemed modified to the extent necessary to make it enforceable by such court or
agency. If any such provision is not enforceable as set forth in the preceding
sentence, the unenforceability of such provision shall not affect the other
provisions of this Warrant, but this Warrant shall be construed as if such
unenforceable provision had never been contained herein.

               18. Headings. The headings of the Sections of this Warrant are
for convenience of reference only and shall not, for any purpose, be deemed a
part of this Warrant.



                                      -18-
<PAGE>   19
               IN WITNESS WHEREOF, the Issuer has executed this Warrant as of
the day and year first above written.

                                    GREYSTONE DIGITAL TECHNOLOGY, INC.


                                    By:
                                       -----------------------------------------
                                       Name:
                                       Title:



                                      -19-
<PAGE>   20
                                  EXERCISE FORM

[NAME OF ISSUER]

The undersigned _______________, pursuant to the provisions of the within
Warrant, hereby elects to purchase _____ shares of Common Stock of
___________________ covered by the within Warrant.

Dated:                                 Signature
      -------------------                        -------------------------------

                                       Address
                                                 -------------------------------
                                                 -------------------------------


                                   ASSIGNMENT

FOR VALUE RECEIVED, _________________ hereby sells, assigns and transfers unto
__________________ the within Warrant and all rights evidenced thereby and does
irrevocably constitute and appoint _____________, attorney, to transfer the said
Warrant on the books of the within named corporation.

Dated:                                 Signature
                                                 -------------------------------

                                       Address
                                                 -------------------------------
                                                 -------------------------------


                               PARTIAL ASSIGNMENT

FOR VALUE RECEIVED, _________________ hereby sells, assigns and transfers unto
__________________ the right to purchase _________ shares of Warrant Stock
evidenced by the within Warrant together with all rights therein, and does
irrevocably constitute and appoint ___________________, attorney, to transfer
that part of the said Warrant on the books of the within named corporation.

Dated:                                 Signature -------------------------------

                                       Address
                                                 -------------------------------
                                                 -------------------------------

                           FOR USE BY THE ISSUER ONLY:

This Warrant No. W-_____ canceled (or transferred or exchanged) this _____ day
of ___________, _____, shares of Common Stock issued therefor in the name of
_______________, Warrant No. W-_____ issued for ____ shares of Common Stock in
the name of _______________.