<PAGE>

                                                                     Exhibit 4.3

THESE SECURITIES HAVE BEEN ISSUED PURSUANT TO EXEMPTIONS FOR NONPUBLIC OFFERINGS
FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED,
AND APPLICABLE STATE SECURITIES LAWS, AND, ACCORDINGLY, THESE SECURITIES MAY NOT
BE RESOLD OR OTHERWISE DISPOSED OF UNLESS, IN THE OPINION OF COUNSEL FOR OR
SATISFACTORY TO THE ISSUER, REGISTRATION UNDER THE APPLICABLE FEDERAL OR STATE
SECURITIES LAWS IS NOT REQUIRED OR COMPLIANCE IS MADE WITH SUCH REGISTRATION
REQUIREMENTS.

             Void after 5:00 p.m. New York Time, on October 5, 2004

                WARRANT TO PURCHASE 60,651 SHARES OF COMMON STOCK

                                       OF

                               ONESOFT CORPORATION

     This is to certify that, FOR VALUE RECEIVED, DEUTSCHE BANK SECURITIES, INC.
or its registered assigns pursuant to Section (d) hereof ("Holder"), is entitled
to purchase, subject to the provisions of this Warrant, from OneSoft
Corporation, a Delaware corporation (the "Company"), Sixty Thousand Six Hundred
Fifty-One (60,651) fully paid, validly issued and nonassessable shares of Common
Stock, par value $.001 per share, of the Company ("Common Stock"), at the
exercise price of $6.59 per share until October 5, 2004. The number of shares of
Common Stock to be received upon the exercise of this Warrant and the price to
be paid for each share of Common Stock may be adjusted from time to time as
hereinafter set forth. The shares of Common Stock deliverable upon such
exercise, and as adjusted from time to time, are hereinafter sometimes referred
to as "Warrant Shares", and the exercise price of a share of Common Stock as
adjusted from time to time is hereinafter sometimes referred to as the "Exercise
Price."

     (a) EXERCISE OF WARRANT; NOTIFICATION OF EXPIRATION DATE OF WARRANT.  The
Warrant may be exercised as to a minimum of 60,651 Warrant Shares at any time,
until 5:00 P.M. New York time on October 5, 2004 (the "Expiration Date"),
provided, however, that if such day is a day on which banking institutions in
the State of New York are authorized by law to close, then on the next
succeeding day which shall not be such a day.  The Warrant may be exercised by
presentation and surrender hereof to the Company at its principal office, or at
the office of its stock transfer agent, if any, with the Purchase Form annexed
hereto duly executed (with signature guaranteed if required by the Company or
its stock transfer agent) and accompanied by payment of the Exercise Price for
the number of Warrant Shares specified in such form and any applicable taxes.
The purchase price for any Warrant Shares purchased pursuant to the exercise of
this Warrant shall be paid in full upon such exercise in cash or by certified or
bank check or pursuant to a cashless exercise procedure whereby the Warrant
Shares issued upon exercise of this Warrant will be sold with Holder receiving
the difference between the Exercise Price and the sale price, in cash, and the
Company receiving the Exercise Price for the Warrant Shares, in cash, or any
combination of the foregoing methods of paying the Exercise
<PAGE>

Price. In the alternative, the Warrant may be exchanged for Warrant shares as
described in Section (a). As soon as practicable after each such exercise of the
Warrants, but not later than seven (7) business days from the date of such
exercise, the Company shall issue and deliver to the Holder a certificate or
certificates for the Warrant Shares issuable upon such exercise, registered in
the name of the Holder or the Holder's designee, except in the case of a
cashless exercise. If the Warrant should be exercised in part only, the Company
shall, upon surrender of the Warrant for cancellation, execute and deliver a new
Warrant evidencing the rights of the Holder thereof to purchase the balance of
the Warrant Shares purchasable thereunder. In the event of a cash exercise, upon
receipt by the Company of the Warrant at its office, or by the stock transfer
agent of the Company at its office, in proper form for exercise, together with
the exercise price thereof and taxes as aforesaid in cash or certified or bank
check and the investment letter described below, the Holder shall be deemed to
be the holder of record of the shares of Common Stock issuable upon such
exercise, notwithstanding that the stock transfer books of the Company shall
then be closed or that certificates representing such shares of Common Stock
shall not then be physically delivered to the Holder. In order to assure the
availability of an exemption from registration under the federal or applicable
state securities laws, the Company may condition the exercise of the Warrant
upon the Holder delivering to the Company an investment letter in the form as
customarily used by the Company from time to time in connection with the
exercise of non- registered options and warrants which are issued by the
Company. It is further understood that certificates for the Warrant Shares, if
any, to be issued upon exercise of the Warrant may contain a restrictive legend
substantially in accordance with Section (j) hereof.

     (b) RESERVATION OF SHARES. The Company shall at all times reserve for
issuance and/or delivery upon exercise of this Warrant such number of shares of
its Common Stock as shall be required for issuance and delivery upon exercise of
the Warrants. If the Common Stock is or becomes listed on any national
securities exchange or the NASDAQ National Market System, the Company shall also
list such shares on such exchange subject to notice of issuance or maintain the
listing of its Common Stock on the NASDAQ system, as the case may be.

     (c) FRACTIONAL SHARES. No fractional shares or scrip representing
fractional shares shall be issued upon the exercise of the Warrant. With respect
to any fraction of a share called for upon any exercise hereof, the Company
shall pay to the Holder an amount in cash equal to such fraction multiplied by
the current market value of a share, determined as follows:

         (1) If the Common Stock is listed on a national securities exchange or
         admitted to unlisted trading privileges on such exchange or listed for
         trading on the NASDAQ National Market System, the current market value
         shall be the last reported sale price of the Common Stock on such
         exchange or system on the last business day prior to the date of
         exercise of this Warrant or if no such sale is made on such day, the
         average closing bid and asked prices for such day on such exchange or
         system;

         (2) If the Common Stock is not so listed or admitted to unlisted
         trading privileges, the current market value shall be the mean of the
         last reported bid and asked

<PAGE>

          prices reported by the National Quotation Bureau, Inc., on the last
          business day prior to the date of the exercise of this Warrant; or

          (3)  If the Common Stock is not so listed or admitted to unlisted
          trading privileges and bid and asked prices are not so reported, the
          current market value shall be an amount, not less than the book value
          thereof as at the end of the most recent fiscal year of the Company
          ending prior to the date of the exercise of the Warrant, determined in
          such reasonable manner as may be prescribed by the Board of Directors
          of the Company.

     (d)  EXCHANGE, TRANSFER, ASSIGNMENT OR LOSS OF WARRANT. The Warrant is
exchangeable, without expense, at the option of the Holder, upon presentation
and surrender hereof to the Company or at the office of its stock transfer
agent, if any, for other Warrants of different denominations entitling the
Holder thereof to purchase in the aggregate the same number of shares of Common
Stock purchasable hereunder. Subject to Section (j) hereof, the Holder may
transfer or assign the Warrant, in whole or in part and from time to time. Upon
surrender of this Warrant to the Company at its principal office or at the
office of its stock transfer agent, if any, with the Assignment Form annexed
hereto duly executed (with signature guaranteed, if required by the Company or
its stock transfer agent) and funds sufficient to pay any transfer tax, the
Company shall, without charge, execute and deliver a new Warrant in the name of
the assignee or assignees named in such instrument of assignment and this
Warrant shall promptly be canceled. This Warrant may be divided by or combined
with other Warrants which carry the same rights upon presentation hereof at the
principal office of the Company or at the office of its stock transfer agent, if
any, together with a written notice specifying the names and denominations in
which new Warrants are to be issued and signed by the Holder hereof. The term
"Warrant" as used herein includes any Warrants into which this Warrant my be
divided or exchanged. Upon receipt by the Company of evidence satisfactory to it
of the loss, theft, destruction or mutilation of this Warrant, and in the case
of loss, theft or destruction, of reasonable satisfactory indemnification, and
upon surrender and cancellation of this Warrant, if mutilated, the Company will
execute and deliver a new Warrant of like tenor, date and amount. Any such new
Warrant executed and delivered shall constitute an additional contractual
obligation on the part of the Company, whether or not the original Warrant shall
be at any time enforceable by anyone.

     (e)  RIGHTS OF THE HOLDER. The Holder shall not, by virtue hereof, be
entitled to any rights of a shareholder in the Company, either at law or equity,
and the rights of the Holder are limited to those expressed in the Warrant and
are not enforceable against the Company except to the extent set forth herein.

     (f)  ANTI-DILUTION PROVISIONS. So long as this Warrant shall be
outstanding, the Exercise Price in effect at any time and the number and kind of
securities purchasable upon the exercise of the Warrants shall be subject to
adjustment from time to time upon the happening of certain events as follows:
<PAGE>

          (1) In case the Company shall (i) declare a dividend or make a
          distribution on its outstanding shares of Common Stock in shares of
          Common Stock, (ii) issue shares of Common Stock or securities
          convertible into Common Stock (other than shares of Series A
          Convertible Preferred Stock, Series B Convertible Preferred Stock and
          Series C Convertible Preferred Stock issued as of October 5, 1999, and
          Common Stock, stock options, warrants or rights to purchase up to
          4,000,000 shares of Common Stock available for issuance to officers,
          directors and employees of the Company; (iii) subdivide or reclassify
          its outstanding shares of Common Stock into a greater number of
          shares, or (iv) combine or reclassify its outstanding shares of Common
          Stock into a smaller number of shares, the Exercise Price in effect at
          the time of the record date for such dividend or distribution, the
          sale of such securities or the effective date of such subdivision,
          combination or reclassification shall be proportionately adjusted as
          of the effective date of such event by multiplying such Exercise Price
          by a fraction, the denominator of which shall be the number of shares
          of Common Stock outstanding immediately following such event and the
          numerator of which shall be the number of shares of Common Stock
          outstanding immediately prior thereto. For example, if the Company
          declares a 2 for 1 stock distribution and the Exercise Price
          immediately prior to such event was $1.00 per share, the adjusted
          Exercise Price immediately after such event would be $.50 per share.
          Such adjustment shall be made successively whenever any event listed
          above shall occur.

          (2) Whenever the Exercise Price payable upon exercise of each Warrant
          is adjusted pursuant to subsection (A) above, the number of Warrant
          Shares purchasable upon exercise of the Warrant shall simultaneously
          be adjusted by multiplying the number of Warrant Shares issuable upon
          exercise of this Warrant by the Exercise Price in effect on the date
          hereof and dividing the product so obtained by the Exercise Price, as
          adjusted pursuant to subsection (1).

          (3) No adjustment in the Exercise Price shall be required unless such
          adjustment would require an increase or decrease of at least $.05 in
          such price; provided, however, that any adjustments which by reason of
          this subsection (f) (3) are not required to be made shall be carried
          forward and taken into account in any subsequent adjustment required
          to be made hereunder.

          (4) Each computation required by this Section (f) for purposes of
          determining whether the Exercise Price shall be adjusted shall be
          performed by the Company's then engaged firm of independent certified
          public accountants, which shall be a firm of recognized national
          reputation (the "Accounting Firm") on the basis of the Company's
          internally prepared unaudited financial statements. Such unaudited
          financial statements shall be accompanied by a certificate signed by
          the President and Chief Financial Officer certifying that such
          unaudited statements have been prepared in accordance with GAAP on a
          basis consistently applied and included all adjustments (consisting
          only of normal, recurring accruals) necessary for a fair presentation
          of the financial position and results of the Company as of the end
<PAGE>

          each such period. The computations of the Accounting Firm shall be
          final and binding on the Company and the Holder.

          (5) Whenever the Exercise Price is adjusted, as herein provided, the
          Company shall promptly cause a notice setting forth the adjusted
          Exercise Price and adjusted number of Warrant Shares issuable upon
          exercise of each Warrant to be mailed to the Holder, at its address
          appearing in the Warrant Register, and shall cause a certified copy
          thereof to be mailed to its transfer agent, if any.

          (6) All calculations under this Section (f) shall be made to the
          nearest cent or to the nearest Warrant Share, as the case may be.

          (7) In the event that at any time, as a result of an adjustment made
          pursuant to this Section (f) above, the Holder of this Warrant
          thereafter shall become entitled to receive any shares of the Company,
          other than Common Stock, thereafter the number of such other shares so
          receivable upon exercise of this Warrant shall be subject to
          adjustment from time to time in a manner and on terms as nearly
          equivalent as practicable to the provisions with respect to the Common
          Stock contained in subsection (A) above.

          (8) Irrespective of any adjustments in the Exercise Price or the
          number or kind of Warrant Shares purchasable upon exercise of this
          Warrant, Warrants theretofore or thereafter issued may continue to
          express the same price and number and kind of shares as are stated in
          the similar Warrants initially issuable pursuant to this Agreement.

     (g)  OFFICER'S CERTIFICATE. Whenever the Exercise Price shall be adjusted
as required by the provisions of the foregoing Section, the Company shall
forthwith file in the custody of its Secretary or an Assistant Secretary at its
principal office and with its stock transfer agent, if any, an officer's
certificate showing the adjusted Exercise Price determined as herein provided,
setting forth in reasonable detail the facts requiring such adjustment,
including a statement of the number of additional shares of Common Stock, if
any, and such other facts as shall be necessary to show the reason for and the
manner of computing such adjustment. Each such officer's certificate shall be
made available at all reasonable times for inspection by the Holder or any
holder of a Warrant executed and/or delivered pursuant to Section (a) or Section
(d), and the Company shall, forthwith after each such adjustment, mail, by
certified mail, a copy of such certificate to the Holder or any such holder.

     (h)  NOTICES TO WARRANT HOLDERS. So long as this Warrant shall be
outstanding, (i) if the Company shall pay any dividend or make any distribution
upon the Common Stock, or (ii) if the Company shall offer to the holders of
Common Stock for subscription or purchase by them any shares of any class or any
other rights, or (iii) if any capital reorganization of the Company,
reclassification of the capital stock of the Company, consolidation or merger of
the Company with or into another corporation, sale, lease or transfer of all or
substantially all of the property and assets of the Company to another
corporation, or
<PAGE>

voluntary or involuntary dissolution, liquidation or winding up of the Company
shall be effected, then in any such case, the Company shall cause to be mailed
by certified mail to the Holder or any holder of a Warrant executed and/or
delivered pursuant to Section (a) or Section (d), at least 15 days prior to the
date specified in (x) or (y) below, as the case may be, a notice containing a
brief description of the proposed action and stating the date on which (x) a
record is to be taken for the purpose of such dividend, distribution or rights,
or (y) such reclassification, reorganization, consolidation, merger, conveyance,
lease, dissolution, liquidation or winding up is to take place and the date, if
any is to be fixed, as of which the holders of Common Stock or other securities
shall receive cash or other property deliverable upon such reclassification,
reorganization, consolidation, merger, conveyance, dissolution, liquidation or
winding up.

     (i)  RECLASSIFICATION, REORGANIZATION OR MERGER. In case of any
reclassification or capital reorganization of outstanding shares of Common Stock
of the Company, or in case of any consolidation or merger of the Company with or
into another corporation (other than a merger with another corporation in which
merger the Company is the continuing corporation and which does not result in
any reclassification or capital reorganization of outstanding shares of Common
Stock of the class issuable upon exercise of this Warrant) or in case of any
sale, lease or conveyance to another corporation of the property of the Company
as an entirety, the Company shall, as a condition precedent to such transaction,
cause effective provisions to be made so that the Holder or any holder of a
Warrant executed and/or delivered pursuant to Section (a) or Section (d) shall
have the right thereafter by exercising the Warrant at any time prior to the
expiration of the Warrant, to purchase the kind and amount of shares of stock
and other securities and property receivable upon such reclassification or
capital reorganization and consolidation, merger, sale or conveyance. Any such
provision shall include provision for adjustments which shall be as nearly
equivalent as may be practicable to the adjustments provided for in the Warrant.
The foregoing provisions of this Section (i) shall similarly apply to successive
reclassifications or capital reorganizations of shares of Common Stock and to
successive consolidations, mergers, sales or conveyances. In the event that in
connection with any such capital reorganization or reclassification,
consolidation, merger, sale or conveyance, additional shares of Common Stock
shall be issued in exchange, conversion, substitution or payment, in whole or in
part, for a security of the Company other than Common Stock, any such issue
shall be treated as an issue of Common Stock covered by the provisions of
subsection (1) of Section (f) hereof.

     (j)  SECURITIES LAW COMPLIANCE

          (1) The Holder of the Warrant, by acceptance hereof, acknowledges that
          the Warrant and the shares of Common Stock to be issued upon exercise
          hereof or conversion thereof 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, transfer, assign
          or otherwise dispose of this Warrant or any shares of Common Stock to
          be issued upon exercise hereof or conversion thereof except under
          circumstances that will not result in a violation of the Act or any
          state securities laws. Upon exercise of the Warrant, the Holder shall,
          if requested by the Company, confirm in writing, in a form
          satisfactory to the Company, that the
<PAGE>

          shares of Common Stock so purchased are being acquired solely for the
          Holder's own account and not as a nominee for any other party, for
          investment, and not with a view toward distribution or resale.

               (2) If appropriate, the Warrant and any Warrants issued upon
          exercise or substitution or upon assignment or transfer pursuant to
          Section (a) or Section (d), as the case may be, and all shares of
          Common Stock issued upon exercise hereof or conversion thereof shall
          be stamped or imprinted with legends setting forth the restrictions on
          transfer arising under applicable federal and state securities laws.

     (k)  REGISTRATION RIGHTS UNDER THE SECURITIES ACT OF 1933

          (1) Commencing the date hereof, the Company shall advise the Holder of
          the Warrant or of the Warrant Shares or any then Holder of Warrants or
          Warrant Shares (such persons being collectively referred to herein as
          "Holders") by written notice at least 21 days prior to the filing of
          any registration statement or post-effective amendment thereto
          ("Registration Statement") under the Securities Act of 1933, as
          amended (the "Act"), covering an underwritten public offering of
          equity securities of the Company and shall register in any such
          Registration Statement the number of Warrant Shares that the Holder
          shall notify the Company it desires to register and shall include in
          any such Registration Statement such information as may be required to
          permit a public offering of such Warrant Shares by the Company's
          underwriter(s). The Company shall supply prospectuses and other
          documents as the Holder may reasonably request in order to facilitate
          the public sale or other disposition of the Warrant Shares. The
          Company shall bear the entire cost and expense of a registration of
          securities initiated by it under this Paragraph (1). The Holder shall,
          however, bear the fees of its own counsel and any transfer taxes and
          underwriting discounts or commissions applicable to the Warrant Shares
          sold by it. The Company may include other securities in any such
          registration statement. The Company shall do any and all other acts
          and things which may be necessary or desirable to enable the Holder to
          consummate the public sale or other disposition of the Warrant Shares,
          and furnish indemnification in the manner as set forth in Paragraph
          (2) (a) of this Section (k), but shall not be required to qualify as a
          foreign corporation to qualify the Warrant Shares for sale under the
          securities laws of any state. The Holder shall furnish information and
          indemnification as set forth in Paragraph (2) (b) of this Section (k).
          All decisions as to whether and when to proceed with any Registration
          Statement shall be made solely by the Company.

          Nothwithstanding the foregoing paragraph, in the event that there is
          an underwritten offering of the Company's securities offered pursuant
          to said registration statement pursuant to the immediately preceding
          Paragraph, the underwriter(s) shall have the right to refuse to permit
          any Warrant Shares, or to limit the amount of Warrant Shares, to be
          sold by the Holder to such
<PAGE>

          underwriter(s) as such underwriter(s) may determine in its discretion,
          and the Holder shall refrain from selling such remainder of its
          Warrant Shares covered by such registration statement for the period
          of one hundred eighty (180) days following the effective date and
          shall also refrain at any time when notified by the Company that an
          amendment or supplement to the prospectus is required. The Company
          shall not be obligated to keep any Registration Statement effective
          for a total of more than thirty (30) days.

          (2) (a) Whenever pursuant to this Section (k) a Registration Statement
          relating to the Warrant Shares is filed under the Act, amended or
          supplemented, the Company will indemnify and hold harmless each Holder
          of Warrant Shares covered by such Registration Statement, amendment or
          supplement (such Holder being hereinafter called the "Distributing
          Holder"), and each person, if any who controls (within the meaning of
          the Act) the Distributing Holder, against any losses, claims, damages
          or liabilities, joint or several, to which the Distributing Holder or
          any such controlling person may become subject, under the Act or
          otherwise, insofar as such losses, claims, damages or liabilities (or
          actions in respect thereof) arise out of or are based upon any untrue
          statement or alleged untrue statement of any material fact contained
          in any such Registration Statement or any preliminary prospectus or
          final prospectus constituting a part thereof or any amendment or
          supplement thereto, or arise out of or are based upon the omission to
          state therein a material fact required to be stated therein or
          necessary to make the statements therein not misleading; and will
          reimburse the Distributing Holder and each such controlling person for
          any legal or other expenses reasonably incurred by the Distributing
          Holder and each controlling person for any legal or other expenses
          reasonable incurred by the Distributing Holder or such controlling
          person or underwriter in connection with investigating or defending
          any such loss, claim, damage, liability or action; provided, however,
          that the Company will not be liable in any such case to the extent
          that any such loss, claim, damage or liability arises out of or is
          based upon an untrue statement or alleged untrue statement or omission
          or alleged omission made in said Registration Statement, preliminary
          prospectus, final prospectus or amendment or supplement, in reliance
          upon and in conformity with written information furnished by the
          Distributing Holder or underwriter for use in the preparation thereof.

          (b)  The Distributing Holder will indemnify and hold harmless the
          Company, each of its directors, each of its officers who have signed
          said Registration Statement and such amendments and supplements
          thereto, each person, if any, who controls the Company (within the
          meaning of the Act) and the Company's underwriter(s) and each person,
          if any, who controls such underwriter(s) (within the meaning of the
          Act) against any losses, claims, damages or liabilities to which the
          Company or any such director, officer, underwriter or controlling
          person may become subject, under the Act or otherwise, insofar as such
          losses, claims, damages or liabilities arise out of or are based upon
          any untrue or alleged untrue statement of any material fact contained
          in said Registration Statement, preliminary
<PAGE>

          prospectus, final prospectus, or amendment or supplement, or arise out
          of or are based upon the omission or the alleged omission to state
          therein a material fact required to be stated therein or necessary to
          make the statements therein not misleading, in each case to the
          extent, but only to the extent that such untrue statement or alleged
          untrue statement or omission or alleged omission was made in said
          Registration Statement, preliminary prospectus, final prospectus or
          amendment or supplement, in reliance upon and in conformity with
          written information furnished by such Distributing Holder for use in
          the preparation thereof; and will reimburse the Company or underwriter
          or any such director, officer or controlling person for any legal or
          other expenses reasonably incurred by them in connection with
          investigating or defending any such loss, claim, damage, liability or
          action.

          (c) Promptly after receipt by an indemnified party under this
          Paragraph 2 of notice of the commencement of any action, such
          indemnified party will, if a claim in respect thereof is to be made
          against any indemnifying party, give the indemnifying party notice of
          the commencement thereof; but the omission so to notify the
          indemnifying party will not relieve it from any liability which it may
          have to any indemnified party otherwise than under this Paragraph 2.

          (d) In case any such action is brought against any indemnified party,
          and it notifies an indemnifying party of the commencement thereof, the
          indemnifying party will be entitled to participate in, and, the extent
          that it may wish, jointly with any other indemnifying party similarly
          notified to assume the defense thereof, with counsel reasonably
          satisfactory to such indemnified party, and after notice from the
          indemnifying party to such indemnified party of its election so to
          assume the defense thereof, the indemnifying party will not be liable
          to such indemnified party under this Paragraph 2 for any legal or
          other expenses subsequently incurred by such indemnified party in
          connection with the defense thereof other than reasonable costs of
          investigation.

          (e) The Company's agreements with respect to Warrant Shares in this
          Section (k) shall continue in effect regardless of the exercise or
          surrender of the Warrant.

     (1)  RIGHT TO CONVERT WARRANT INTO COMMON STOCK.

          (1) Right to Convert. The Holder shall have the right to require the
              ----------------
          Company to convert this Warrant provided in this Section (1), into
          common stock (the "Net Conversion Right"). Upon exercise of the Net
          Conversion Right, the Company shall deliver to the Holder (without
          payment by the Holder of any Exercise Price or of any other cash or
          consideration) that number of shares of Common Stock equal to the
          quotient obtained by dividing (x) the value of this Warrant at the
          time the Conversion Right is exercised (determined by subtracting the
          aggregate Exercise Price in effect immediately prior to the exercise
          of the Conversion Right from the aggregate fair market value of the
          shares of Common Stock issuable
<PAGE>

          upon exercise of this Warrant immediately prior to the exercise of the
          Conversion Right) by (y) the fair market value of one share of Common
          Stock immediately prior to the exercise of the Conversion Right.

          (2) Method of Exercise. The Net Conversion Right may be exercised by
              ------------------
          the Holder by the surrender of this Warrant at the principal office of
          the Company together with a written statement specifying that the
          Holder thereby intends to exercise the Net Conversion Right.
          Certificates for the shares of Common Stock issuable upon exercise of
          the Net Conversion Right shall be delivered to the Holder within five
          (5) days following the Company's receipt of this Warrant together with
          the aforesaid written statement.

          (3) Determination of Fair Market Value.  For purposes of this Section
              ----------------------------------
          (f), fair market value of a share of Common Stock as of a particular
          date (the "Determination Date") shall be determined in accordance with
          Section (c) of this Warrant.

     (m)  AMENDMENTS. Neither the Warrant nor any term hereof may be changed,
waived, discharged or terminated without the prior written consent of the
Holder.

     (n)  NO IMPAIRMENT. The Company will not avoid or seek to avoid the
observance or performance of any of the terms to be observed or performed
hereunder by the Company, but will at all times in good faith assist in the
carrying out of all the provisions of this Warrant and in the taking of all such
action as may be necessary or appropriate in order to protect the rights of any
Holder.

     (o)  GOVERNING LAW. This Agreement shall be governed by and construed under
the laws of the State of Delaware.

     (p)  NOTICES. All notices and other communications required or permitted
hereunder shall be in writing and shall be mailed by first class mail, postage
prepaid, addressed (a) if to the Holder, to Deutsche Bank Securities, Inc., 1
South Street, Baltimore, Maryland 21202, Attention: Geoffrey Stengel, III, or
(b) if to the Company, to OneSoft Corporation, 1505 Farm Credit Drive, McLean,
Virginia 22102, Attention: James W. MacIntyre, IV, or at such other address as
to the Company shall have furnished to the Holder in writing.
<PAGE>

     IN WITNESS WHEREOF, OneSoft Corporation has caused this Warrant to be
executed by its officer thereunto duly authorized.

Dated:  October 5, 1999

                                    ONESOFT CORPORATION


                                    By: /s/ James W. MacIntyre, IV
                                       ---------------------------
                                    Name: James W. MacIntyre, IV
                                         -------------------------
                                    Title: President
                                          ------------------------
<PAGE>

                                  PURCHASE FORM
                                  -------------



                                           Dated _______________, 19___


     The undersigned hereby irrevocably elects to exercise its rights pursuant
to this Warrant to the extent of purchasing ______ shares of Common Stock of
OneSoft Corporation, and hereby makes payment of $___________, in cash, in
payment of the exercise price thereof.

     [The undersigned hereby irrevocably elects to exercise its rights pursuant
to this Warrant to the extent of purchasing _____ shares of Common Stock and
hereby authorizes you to deliver such shares of Common Stock for sale to
___________, and to retain from the proceeds of such sale $__________, in cash,
in payment of the exercise price thereof and to remit to the undersigned the
balance of such proceeds.]


                                -----------------


                     INSTRUCTIONS FOR REGISTRATION OF STOCK
                     --------------------------------------


Name_____________________________________________________________
          (Please typewrite or print in block letters)


Address__________________________________________________________

Signature________________________________________________________
<PAGE>

                                 ASSIGNMENT FORM
                                 ---------------


     FOR VALUE RECEIVED, _________________________________________
hereby sells, assigns and transfers unto


Name______________________________________________________________
          (Please typewrite or print in block letters)

Address___________________________________________________________

the right to purchase Common Stock of OneSoft Corporation (the "Company"),
represented by this Warrant to the extent of __________ shares as to which such
right is exercisable and does hereby irrevocably constitute and appoint
_____________________________ as Attorney, to transfer the same on the books of
the Company with full power of substitution in the premises.


Date ___________, 19___

Signature__________________________