<PAGE>
                                                                    EXHIBIT 3.33

                  CERTIFICATE OF DETERMINATION OF PREFERENCES
                                       OF
                            SERIES FF PREFERRED STOCK
                                       OF
                                   DISC, INC.

        We, Robert W. Riland III and Henry Madrid, hereby certify that we are
the President and the Chief Financial Officer, respectively, of DISC, INC., a
corporation organized and existing under the General Corporation Law of the
State of California, and further, DO HEREBY CERTIFY:

        That pursuant to the authority conferred upon the Board of Directors by
the Articles of Incorporation of the said Corporation, the said Board of
Directors on December 4, 2001 adopted the following resolution creating a series
of 51,546 shares of Preferred Stock designated as Series FF Preferred Stock,
none of which shares have been issued:

               "RESOLVED, that pursuant to the authority vested in the Board of
        Directors of the corporation by the Articles of Incorporation, the Board
        of Directors does hereby provide for the issuance of a series of
        Preferred Stock, no par value, of the Corporation, to be designated
        "Series FF Preferred Stock," initially consisting of 51,546 shares and
        to the extent that the designations, powers, preferences and relative
        and other special rights and the qualifications, limitations and
        restrictions of the Series FF Preferred Stock are not stated and
        expressed in the Articles of Incorporation, does hereby fix and herein
        state and express such designations, powers, preferences and relative
        and other special rights and the qualifications, limitations and
        restrictions thereof, as follows (all terms used herein which are
        defined in the Articles of Incorporation shall be deemed to have the
        meanings provided therein):

               Section 1. Designation and Amount. The shares of such series
        shall be designated as "Series FF Preferred Stock," no par value, and
        the number of shares constituting such series shall be 51,546.

               Section 2. Dividends and Distributions.

                    (A) Subject to the prior and superior right of the holders
        of any shares of Series C Preferred Stock ranking prior and superior to
        the shares of Series FF Preferred Stock with respect to dividends, and
        pari passu with the rights of the holders of shares of Series D
        Preferred Stock, Series E Preferred Stock, Series F Preferred Stock,
        Series G Preferred Stock, Series H Preferred Stock, Series I Preferred
        Stock, Series J Preferred Stock, Series K Preferred Stock, Series L
        Preferred Stock, Series M Preferred Stock, Series N Preferred Stock,
        Series O Preferred Stock, Series P Preferred Stock, Series Q Preferred
        Stock, Series R Preferred Stock, Series S Preferred Stock, Series T
        Preferred Stock, Series U Preferred Stock, Series V Preferred Stock,
        Series W Preferred Stock, Series X Preferred Stock, Series Y Preferred
        Stock, Series Z Preferred Stock, Series AA Preferred Stock, Series BB
        Preferred Stock, Series CC Preferred stock, Series DD Preferred Stock,
        and Series EE Preferred stock, with respect to dividends, subject to the
        rights of any series of Preferred Stock which may hereafter come into
        existence, the holders of shares of Series FF Preferred Stock shall be
        entitled to receive when, as and if declared by the Board of Directors
        out of funds legally available for the purpose, dividends in the same
        amount per share as declared on the Common Stock, treating such number
        of shares of Series FF Preferred Stock for this purpose

<PAGE>

        as equal to the number of shares of Common Stock into which it is then
        convertible. In the event any dividends are declared or paid on the
        outstanding shares of Series D Preferred Stock, Series E Preferred
        Stock, Series F Preferred Stock, Series G Preferred Stock, Series H
        Preferred Stock, Series I Preferred Stock, Series J Preferred Stock,
        Series K Preferred Stock, Series L Preferred Stock, Series M Preferred
        Stock, Series N Preferred Stock, Series O Preferred Stock, Series P
        Preferred Stock, Series Q Preferred Stock, Series R Preferred Stock,
        Series S Preferred Stock, Series T Preferred Stock, Series U Preferred
        Stock, Series V Preferred Stock, Series W Preferred Stock, Series X
        Preferred Stock, Series Y Preferred Stock, Series Z Preferred Stock,
        Series AA Preferred Stock, Series BB Preferred Stock, Series CC
        Preferred Stock, Series DD Preferred Stock, and Series EE Preferred
        Stock, dividends shall simultaneously be declared and paid on the
        outstanding shares of Series FF Preferred Stock, pari passu with the
        shares of Series D Preferred Stock, Series E Preferred Stock, Series F
        Preferred Stock, Series G Preferred Stock, Series H Preferred Stock,
        Series I Preferred Stock, Series J Preferred Stock, Series K Preferred
        Stock, Series L Preferred Stock, Series M Preferred Stock, Series N
        Preferred Stock, Series O Preferred Stock, Series P Preferred Stock,
        Series Q Preferred Stock, Series R Preferred Stock, Series S Preferred
        Stock, Series T Preferred Stock, Series U Preferred Stock, Series V
        Preferred Stock, Series W Preferred Stock, Series X Preferred Stock,
        Series Y Preferred Stock, Series Z Preferred Stock, Series AA Preferred
        Stock, Series BB Preferred Stock, Series CC Preferred Stock, Series DD
        Preferred Stock, and Series EE Preferred Stock based upon the number of
        shares of Common Stock into which shares of Series D Preferred Stock,
        Series E Preferred Stock, Series F Preferred Stock, Series G Preferred
        Stock, Series H Preferred Stock, Series I Preferred Stock, Series J
        Preferred Stock, Series K Preferred Stock, Series L Preferred Stock,
        Series M Preferred Stock, Series N Preferred Stock, Series O Preferred
        Stock, Series P Preferred Stock, Series Q Preferred Stock, Series R
        Preferred Stock, Series S Preferred Stock, Series T Preferred Stock,
        Series U Preferred Stock, Series V Preferred Stock, Series W Preferred
        Stock, Series X Preferred Stock, Series Y Preferred Stock, Series Z
        Preferred Stock, Series AA Preferred Stock, Series BB Preferred Stock,
        Series CC Preferred Stock, Series DD Preferred Stock, Series EE
        Preferred Stock, and Series FF Preferred Stock are then convertible. In
        the event the Corporation shall at any time after the date of the filing
        of this Certificate of Determination of Preferences (the "Rights
        Declaration Date") (i) declare any dividend on Common Stock payable in
        shares of Common Stock, (ii) subdivide the outstanding Common Stock, or
        (iii) combine the outstanding Common Stock into a smaller number of
        shares, then in each such case, the amount of Common Stock or other
        consideration to which holders of shares of Series FF Preferred Stock
        were entitled immediately prior to such event under the preceding
        sentence shall be adjusted as set forth in Section 4(C) hereof.

                    (B) The Corporation shall declare a dividend or distribution
        on the Series FF Preferred Stock as provided in paragraph (A) above
        prior to declaring a dividend payable on shares of Common Stock.

               Section 3. Voting Rights. The holders of shares of Series FF
        Preferred Stock shall have the following voting rights:

                    (A) Each holder of Series FF Preferred Stock is entitled to
        a number of votes equal to the number of shares of Common Stock into
        which the holder's Series FF Preferred Stock is then convertible. Except
        as provided by law, the Common Stock and Series FF Preferred Stock (and
        any series of Preferred Stock which may be subsequently


                                       2
<PAGE>

        authorized which is convertible into shares of Common Stock and which
        has voting rights equal to the number of shares of Common Stock into
        which such series of Preferred Stock is then convertible) shall vote
        together as a single class on all matters to come before the
        shareholders for approval. In the event the Corporation shall at any
        time after the Rights Declaration Date (i) declare any dividend on
        Common Stock payable in shares of Common Stock, (ii) subdivide the
        outstanding Common Stock, or (iii) combine the outstanding Common Stock
        into a smaller number of shares, then in each such case the number of
        votes per share to which holders of shares of Series FF Preferred Stock
        were entitled immediately prior to such event shall be adjusted as set
        forth in Section 4(C) hereof.

                    (B) Except as otherwise provided herein or by law, the
        holders of shares of Series FF Preferred Stock and the holders of shares
        of Common Stock (and any series of Preferred Stock which may be
        subsequently authorized which is convertible into shares of Common Stock
        and which has voting rights equal to the number of shares of Common
        Stock into which such series of Preferred Stock is then convertible)
        shall vote together as one class on all matters submitted to a vote of
        shareholders of the Corporation.

                    (C) Except as required by law or under Section 8 hereof,
        holders of Series FF Preferred Stock shall have no special voting rights
        and their consent shall not be required (except to the extent they are
        entitled to vote with holders of Common Stock as set forth herein) for
        taking any corporate action.

               Section 4. Conversion Rights.

                    (A) Each holder of Series FF Preferred Stock may, at any
        time, in such holder's sole discretion, convert all or any part of such
        holder's shares of Series FF Preferred Stock into fully paid and
        nonassessable shares of Common Stock at the rate of ten (10) shares of
        Common Stock for each share of Series FF Preferred Stock surrendered for
        conversion.

                    (B) Such conversion may be effected by surrender of such
        holder's certificate or certificates for the shares of Series FF
        Preferred Stock to be converted, duly endorsed, at the principal office
        of the Corporation, with a written notice stating (i) that such holder
        elects to convert all or a specified number of shares of Series FF
        Preferred Stock into shares of Common Stock, and (ii) the name in which
        such holder desires a certificate for the shares of Common Stock to be
        issued. Promptly thereafter, the Company shall issue and deliver to such
        holder a certificate for the number of shares of Common Stock to which
        such holder shall be entitled. Such conversion shall be deemed to have
        been made at the close of business on the date of such surrender, and
        such holder shall be treated for all purposes as the record holder of
        such shares of Common Stock on that date.

                    (C) In the event the Corporation shall at any time after the
        Rights Declaration Date (i) declare any dividend on Common Stock payable
        in shares of Common Stock, (ii) subdivide the outstanding Common Stock,
        or (iii) combine the outstanding Common Stock into a smaller number of
        shares, then, in each case, the number of shares of Common Stock
        issuable upon the conversion of each share of Series FF Preferred Stock
        shall be adjusted by multiplying such amount by a fraction, the
        numerator of which is the number of shares of Common Stock outstanding
        immediately after such event and the denominator of which is the number
        of shares of Common Stock that are outstanding immediately prior to such
        event.


                                       3
<PAGE>

                    (D) In the event the Corporation shall at any time or from
        time to time after the Rights Declaration Date make or issue, or fix a
        record date for the determination of holders of Common Stock entitled to
        receive, a dividend or other distribution payable in securities of the
        Corporation or any of its subsidiaries, or of any other corporation or
        third party, other than in shares of Common Stock, then, in each such
        event, provisions shall be made so that the holders of Series FF
        Preferred Stock shall receive, upon the conversion thereof, securities
        of the Corporation or any of its subsidiaries or of any other
        corporation or third party which they would have received had their
        stock been converted into Common Stock on the date of such event.

               Section 5. Reacquired Shares. Any shares of Series FF Preferred
        Stock purchased or otherwise acquired by the Corporation in any manner
        whatsoever shall be retired and canceled promptly after the acquisition
        thereof. All such shares shall upon their cancellation become authorized
        but unissued shares of Preferred Stock and may be reissued as part of a
        new series of Preferred Stock to be created by resolution or resolutions
        of the Board of Directors, subject to the conditions and restrictions on
        issuance set forth herein.

               Section 6. Liquidation, Dissolution or Winding Up.

                    (A) Upon any liquidation (voluntary or otherwise),
        dissolution or winding up of the Corporation, following the first
        priority liquidation preference of the Series C Preferred Stock in the
        amount of $5.00 per share plus any declared but unpaid dividends, and
        pari passu with the liquidation preference of the Series D Preferred
        Stock in the amount of $5.00 per share plus any declared but unpaid
        dividends ("Series D Liquidation Preference"), the liquidation
        preference of the Series E Preferred Stock in the amount of $4.00 per
        share plus any declared but unpaid dividends ("Series E Liquidation
        Preference"), the liquidation preference of the Series F Preferred Stock
        in the amount of $8.00 per share plus any declared but unpaid dividends
        ("Series F Liquidation Preference"), the liquidation preference of the
        Series G Preferred Stock in the amount of $20.00 per share plus any
        declared but unpaid dividends ("Series G Liquidation Preference"), the
        liquidation preference of the Series H Preferred Stock in the amount of
        $38.30 per share plus any declared but unpaid dividends ("Series H
        Liquidation Preference"), the liquidation preference of the Series I
        Preferred Stock in the amount of $4.19 per share plus any declared but
        unpaid dividends ("Series I Liquidation Preference"), the liquidation
        preference of the Series J Preferred Stock in the amount of $2.98 per
        share plus any declared but unpaid dividends ("Series J Liquidation
        Preference"), the liquidation preference of the Series K Preferred Stock
        in the amount of $3.19 per share plus any declared but unpaid dividends
        ("Series K Liquidation Preference"), the liquidation preference of the
        Series L Preferred Stock in the amount of $2.76 per share plus any
        declared but unpaid dividends ("Series L Liquidation Preference"), the
        liquidation preference of the Series M Preferred Stock in the amount of
        $2.23 per share plus any declared but unpaid dividends ("Series M
        Liquidation Preference"), the liquidation preference of the Series N
        Preferred Stock in the amount of $.90 per share plus any declared but
        unpaid dividends ("Series N Liquidation Preference"), the liquidation
        preference of the Series O Preferred Stock in the amount of $1.06 per
        share plus any declared but unpaid dividends ("Series O Liquidation
        Preference"), the liquidation preference of the Series P Preferred Stock
        in the amount of $8.20 per share plus any declared but unpaid dividends
        ("Series P Liquidation Preference"), the liquidation preference of the
        Series Q Preferred Stock in the amount of $6.20 per share plus any
        declared but unpaid dividends ("Series Q Liquidation Preference"), the
        liquidation preference of the Series R Preferred Stock in the


                                       4
<PAGE>

        amount of $5.80 share plus any declared but unpaid dividends ("Series R
        Liquidation Preference"), the liquidation preference of the Series S
        Preferred Stock in the amount of $3.20 per share plus any declared but
        unpaid dividends ("Series S Liquidation Preference"), the liquidation
        preference of the Series T Preferred Stock in the amount of $20.20 per
        share plus any declared but unpaid dividends ("Series T Liquidation
        Preference"), the liquidation preference of the Series U Preferred Stock
        in the amount of $15.40 per share plus any declared but unpaid dividends
        ("Series U Liquidation Preference"), the liquidation preference of the
        Series V Preferred Stock in the amount of $10.60 per share plus any
        declared but unpaid dividends ("Series V Liquidation Preference"), the
        liquidation preference of the Series W Preferred Stock in the amount of
        $14.90 per share plus any declared but unpaid dividends ("Series W
        Liquidation Preference"), the liquidation preference of the Series X
        Preferred Stock in the amount of $25.00 per share plus any declared but
        unpaid dividends ("Series X Liquidation Preference"), the liquidation
        preference of the Series Y Preferred Stock in the amount of $19.10 per
        share plus any declared but unpaid dividends ("Series Y Liquidation
        Preference"), the liquidation preference of the Series Z Preferred Stock
        in the amount of $21.30 per share plus any declared but unpaid dividends
        ("Series Z Liquidation Preference"), the liquidation preference of the
        Series AA Preferred Stock in the amount of $18.10 per share plus any
        declared but unpaid dividends ("Series AA Liquidation Preference"), the
        liquidation preference of the Series BB Preferred Stock in the amount of
        $18.30 per share plus any declared but unpaid dividends ("Series BB
        Liquidation Preference"), the liquidation preference of the Series CC
        Preferred Stock in the amount of $16.20 per share plus any declared but
        unpaid dividends ("Series CC Liquidation Preference"), the liquidation
        preference of the Series DD Preferred Stock in the amount of $20.00 per
        share plus any declared but unpaid dividends ("Series DD Liquidation
        Preference"), and the liquidation preference of the Series EE Preferred
        Stock in the amount of $11.10 per share plus any declared but unpaid
        dividends ("Series EE Liquidation Preference"), no distribution shall be
        made to the holders of shares of stock ranking junior (either as to
        dividends or upon liquidation, dissolution or winding up) to the Series
        FF Preferred Stock unless, prior thereto, the holders of shares of
        Series FF Preferred Stock shall have received an amount equal to $9.70
        per share of Series FF Preferred Stock plus any declared but unpaid
        dividends ("Series FF Liquidation Preference").

                    (B) In the event, however, that there are not sufficient
        assets available to permit payment in full of the Series D Liquidation
        Preference, the Series E Liquidation Preference, the Series F
        Liquidation Preference, the Series G Liquidation Preference, the Series
        H Liquidation Preference, the Series I Liquidation Preference, the
        Series J Liquidation Preference, the Series K Liquidation Preference,
        the Series L Liquidation Preference, the Series M Liquidation
        Preference, the Series N Liquidation Preference, the Series O
        Liquidation Preference, the Series P Liquidation Preference, the Series
        Q Liquidation Preference, the Series R Liquidation Preference, the
        Series S Liquidation Preference, the Series T Liquidation Preference,
        the Series U Liquidation Preference, the Series V Liquidation
        Preference, the Series W Liquidation Preference, the Series X
        Liquidation Preference, the Series Y Liquidation Preference, the Series
        Z Liquidation Preference, the Series AA Liquidation Preference, the
        Series BB Liquidation Preference, the Series CC Liquidation Preference,
        the Series DD Liquidation Preference, the Series EE Liquidation
        Preference, and the Series FF Liquidation Preference and the liquidation
        preferences of all other series of Preferred Stock, if any, which rank
        on a parity with the Series FF Preferred Stock, then such remaining
        assets shall be distributed ratably to the holders of such parity shares
        in proportion to their respective liquidation preferences.


                                       5
<PAGE>

               Section 7. No Redemption. The shares of Series FF Preferred Stock
        shall not be redeemable.

               Section 8. Amendment. The Articles of Incorporation of the
        Corporation shall not be further amended in any manner which would (a)
        alter or change the powers, preferences or special rights or privileges
        of the Series FF Preferred Stock so as to affect them adversely or (b)
        grant to any other class of shares any rights superior to those of the
        Series FF Preferred Stock without the affirmative vote of the holders of
        a majority or more of the outstanding shares of Series FF Preferred
        Stock, voting separately as a class.

               Section 9. Fractional Shares. Series FF Preferred Stock may be
        issued in fractions of a share which shall entitle the holder, in
        proportion to such holder's fractional shares, to exercise voting
        rights, receive dividends, participate in distributions and to have the
        benefit of all other rights of holders of Series FF Preferred Stock."

        The undersigned declare under penalty of perjury that the matters set
forth in the foregoing Certificate are true of their own knowledge.

        Executed at Milpitas, California on April 15, 2002.

                                           /s/  Robert W. Riland III
                                           -------------------------------------
                                           Robert W. Riland III
                                           President and Chief Executive Officer


                                           /s/  Henry Madrid
                                           -------------------------------------
                                           Henry Madrid
                                           Chief Financial Officer


                                       6