Document:

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                                                                  Exhibit 10.7

                             UNCONDITIONAL GUARANTY

         For and in consideration of certain loans by SILICON VALLEY BANK, a
California-chartered bank, with its principal place of business at 3003 Tasman
Drive, Santa Clara, California 95054 and with a loan production office located
at One Newton Executive Park, Suite 200, 2221 Washington Street, Newton,
Massachusetts 02462, doing business under the name "Silicon Valley East"
("Bank") to ASPEN TECHNOLOGY, INC., a Delaware corporation, ASPENTECH, INC., a
Texas corporation and HYPROTECH COMPANY, a company organized under the laws of
Nova Scotia, Canada (collectively, "Borrower") , which loans were made pursuant
to a certain Loan and Security Agreement and Export-Import Loan and Security
Agreement between Borrower and Bank dated each of even date herewith as each may
be amended from time to time (hereinafter, collectively, the "Agreement"), the
undersigned guarantor, ASPENTECH SECURITIES CORP., a Massachusetts corporation
with its chief executive office located at Ten Canal Park, Cambridge,
Massachusetts 02141 ("Guarantor"), hereby unconditionally and irrevocably
guarantees the prompt and complete payment of all amounts that Borrower owes to
Bank and performance by Borrower of the Agreement and any other agreements now
existing or hereafter arising between Borrower and Bank, as each may be amended
from time to time (collectively referred to as the "Agreements"), in strict
accordance with their respective terms.

         1. If Borrower does not perform its obligations under the Agreements,
Guarantor will, upon demand by Bank, immediately pay all amounts due (including,
without limitation, all principal, interest, and fees) and satisfy all
Borrower's obligations under the Agreements.

         2. These obligations are independent of Borrower's obligations and
separate actions that may be brought against Guarantor (whether action is
brought against Borrower or whether Borrower is joined in the action).
Guarantor's liability is not contingent on the genuineness or enforceability of
the Agreements.

         3. Bank may, without notice to Guarantor and without affecting
Guarantor's obligations under this Guaranty: (a) renew, extend, or otherwise
change the terms of the Agreements; (b) take security for the payment of this
Guaranty or the Agreements; (c) exchange, enforce, waive and release any
security; and (d) apply the security and direct its sale as Bank, in its
reasonable discretion, chooses.

             4. Until all obligations and liabilities of Borrower to Bank have
been paid in full and the Agreements have been terminated, Guarantor waives to
the extent permitted by law:

                (a) Any right to require Bank to: (i) proceed against Borrower
         or any other person; (ii) proceed against or exhaust any security; or
         (iii) pursue any other remedy. Bank may exercise or not exercise any
         right or remedy it has against Borrower or any security it holds
         (including the right to foreclose by judicial or non-judicial sale)
         without affecting Guarantor's liability.

                (b) Any defenses from disability or other defense of Borrower or
         from the cessation of Borrowers liabilities.

                (c) Any right of setoff or right to counterclaim against Bank.

                (d) Any defense from the absence, impairment or loss of any
         right of reimbursement or subrogation or any other rights against
         Borrower. Until Borrower's obligations to Bank have been paid,
         Guarantor has no right of subrogation or reimbursement or subrogation
         or other rights against Borrower.

                (e) Any right to enforce any remedy that Bank has against
         Borrower.

                (f) Any rights to participate in any security held by Bank.

                (g) Any demands for performance, notices of nonperformance or of
         new or additional indebtedness. Guarantor is responsible for being and
         keeping itself informed of Borrower's financial

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condition. Unless Guarantor requests particular information, Bank has no duty to
provide information to Guarantor.

         5. Guarantor acknowledges that, to the extent Guarantor has or may have
rights of subrogation or reimbursement against Borrower for claims arising out
of this Guaranty, those rights may be impaired or destroyed if Bank elects to
proceed against any real property security of Borrower by non-judicial
foreclosure. That impairment or destruction could, under certain judicial cases
and based on equitable principles of estoppel, give rise to a defense by
Guarantor against its obligations under this Guaranty. Guarantor waives that
defense and any others arising from Bank's election to pursue non-judicial
foreclosure.

         6. If Borrower becomes insolvent or is adjudicated bankrupt or files a
petition for reorganization or similar relief under the United States Bankruptcy
Code, or if a petition is filed against Borrower and/or any obligation under the
Agreements is terminated or rejected, or any obligation of Borrower is modified
or if Borrower's obligations are avoided Guarantor's liability will not be
affected and its liability will continue. If Bank must return any payment
because of the insolvency, bankruptcy or reorganization of Borrower, Guarantor
or any other guarantor, this Guaranty will remain effective or be reinstated.

         7. Guarantor subordinates any indebtedness of Borrower it holds to
Bank; and Guarantor will collect, enforce and, upon the occurrence of an Event
of Default, receive payments as Bank's trustee and will pay Bank those payments
without reducing or affecting its liability under this Guaranty.

         8. Guarantor will pay Bank's reasonable attorneys' fees and other costs
and expenses incurred enforcing this Guaranty. This Guaranty may not be waived,
revoked or amended without Bank's prior written consent. If any provision of
this Guaranty is unenforceable, all other provisions remain effective. This
Guaranty represents the entire agreement among the parties about this guaranty.
No prior dealings, no usage of trade, and no parol or extrinsic evidence may
supplement or vary this Guaranty. Bank may assign this Guaranty. This Guaranty
benefits Bank, its successors and assigns. This Guaranty is in addition to any
other guaranties Bank obtains.

         9. Guarantor represents and warrants that (i) it has taken all action
necessary to authorize execute, deliver and perform this Guaranty; (ii)
execution, delivery and performance of this Guaranty do not conflict with any
organizational documents or agreements to which it is a party; and (iii) this
Guaranty is a valid and binding obligation, enforceable against Guarantor
according to its terms.

         10. Guarantor will do all of the following:

             (a) Maintain its corporate existence, remain in good standing in
         Massachusetts, and continue to qualify in each jurisdiction in which
         the failure to qualify could reasonably be expected to have a material
         adverse effect on the financial condition, operations or business.
         Maintain all licenses, approvals, and agreements, the loss of which
         could reasonably be expected to have a material adverse effect on its
         financial condition, operations or business.

             (b) Comply with all statutes and regulations if non-compliance
         could reasonably be expected to adversely and materially affect its
         financial condition, operations or business.

             (c) Execute other instruments and take action Bank reasonably
         requests to effect the purposes of this Agreement.

         11. Guarantor hereby grants to Bank, a lien, security interest and
right of setoff as security for all obligations to Bank, whether now existing or
hereafter arising upon and against all deposits, credits, collateral and
property, now or hereafter in the possession, custody, safekeeping or control of
Bank or any entity under the control of Bank (including a Bank subsidiary) or in
transit to any of them. At any time after the occurrence and during the
continuance of an Event of Default (as defined in the Agreement), without demand
or notice, Bank may set off the same or any part thereof and apply the same to
any liability or obligation of Guarantor even though unmatured and regardless of
the adequacy of any other collateral securing the loan. ANY AND ALL RIGHTS TO
REQUIRE

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BANK TO EXERCISE ITS RIGHTS OR REMEDIES WITH RESPECT TO ANY OTHER COLLATERAL
WHICH SECURES THE LOAN, PRIOR TO EXERCISING ITS RIGHT OF SETOFF WITH RESPECT TO
SUCH DEPOSITS, CREDITS OR OTHER PROPERTY OF THE GUARANTOR, ARE HEREBY KNOWINGLY,
VOLUNTARILY AND IRREVOCABLY WAIVED.

         12. Massachusetts law governs this Guaranty without regard to
principles of conflicts of law. Guarantor and Bank each submit to the exclusive
jurisdiction of the State and Federal courts in Massachusetts; provided,
however, that if for any reason Bank cannot avail itself of such courts in the
Commonwealth of Massachusetts, Guarantor accepts jurisdiction of the courts and
venue in Santa Clara County, California. NOTWITHSTANDING THE FOREGOING, THE BANK
SHALL HAVE THE RIGHT TO BRING ANY ACTION OR PROCEEDING AGAINST THE GUARANTOR OR
ITS PROPERTY IN THE COURTS OF ANY OTHER JURISDICTION WHICH THE BANK REASONABLY
DEEMS NECESSARY OR APPROPRIATE IN ORDER TO REALIZE ON THE COLLATERAL OR TO
OTHERWISE ENFORCE THE BANK'S RIGHTS AGAINST THE GUARANTOR OR ITS PROPERTY.
GUARANTOR AND BANK EACH WAIVE THEIR RIGHT TO A JURY TRIAL OF ANY CLAIM OR CAUSE
OF ACTION ARISING OUT OF OR BASED UPON THIS AGREEMENT, THE LOAN DOCUMENTS OR ANY
CONTEMPLATED TRANSACTION, INCLUDING CONTRACT, TORT, BREACH OF DUTY AND ALL OTHER
CLAIMS. THIS WAIVER IS A MATERIAL INDUCEMENT FOR BOTH PARTIES TO ENTER INTO THIS
AGREEMENT. EACH PARTY HAS REVIEWED THIS WAIVER WITH ITS COUNSEL.

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         IN WITNESS WHEREOF, the undersigned Guarantor has executed this
Guaranty as an instrument under seal under the laws of the Commonwealth of
Massachusetts, as of this 30th day of January, 2003.

                                ASPENTECH SECURITIES CORP.

                                By: /s/ Lisa W. Zappala
                                    -------------------------------------------
                                Name:  Lisa W. Zappala
                                       ----------------------------------------
                                Title: Treasurer
                                       ----------------------------------------

                                       4<PAGE>

                                                                   Exhibit 10.8

                      AMENDMENT NO. 1 TO SECURITY AGREEMENT

         This Amendment No. 1, dated as of January 30, 2003 ("Amendment No. 1"),
to the Security Agreement, dated August 16, 2002 (the "Agreement"), by and
between Accenture LLP, an Illinois general partnership registered as a limited
liability partnership with an office at 1000 Peachtree Street, N.E., Suite 1300,
Atlanta, Georgia 30303 ("Accenture") and Aspen Technology, Inc., a Delaware
corporation with an office at Ten Canal Park, Cambridge, Massachusetts 02141
("AspenTech"), is entered into by and between Accenture and AspenTech. Terms
used and not otherwise defined herein shall have the meanings given them in the
Agreement.

         WHEREAS, the Parties previously entered into the Agreement, pursuant to
which AspenTech granted to Accenture a lien on and security interest in the
Initial Collateral to secure repayment of the Outstanding Debt;

         WHEREAS, pursuant to the Agreement, AspenTech agreed that if it had not
established a Lender's Line of Credit by December 31, 2002, it would grant to
Accenture a lien and security interest in its accounts receivable as specified
in the Agreement and that such accounts receivable would thereafter replace the
Initial Collateral in securing the Outstanding Debt; and

         WHEREAS, the Parties desire to amend the Security Agreement to provide
that Accenture shall have a first priority security interest in certain
installment receivables of AspenTech to secure repayment of the Outstanding
Debt, and that such collateral shall replace the Initial Collateral and any
other security interest to which Accenture otherwise would have been entitled
pursuant to the Agreement;

         NOW, THEREFORE, for good and valuable consideration, the receipt of
which is hereby acknowledged; the each of the Parties hereby agrees as follows:

     1.   Sections 1 through 5 of the Agreement are hereby deleted in their
          entirety and replace with the following sections:

          "1.  To secure the prompt payment of the Outstanding Debt, AspenTech
               hereby grants to Accenture a lien and first priority security
               interest in AspenTech's right, title and interest in and to the
               installment receivables or other rights to receive payment listed
               on SCHEDULE 1 attached hereto together with the proceeds
               therefrom (the "Installment Collateral"). The Parties agree that
               the security interest in the Installment Collateral granted
               hereby replaces and supercedes Accenture's security interest in
               the collateral set forth on EXHIBIT A of the original Agreement
               (the "Original Collateral") and any other security interest to
               which Accenture otherwise would have been entitled pursuant to
               the terms of the original Agreement.

<PAGE>

          2.   AspenTech represents and warrants to Accenture that (i) AspenTech
               is the legal and beneficial owner of the Installment Collateral
               free and clear of all liens, security interests or other
               encumbrances, (ii) there is no dispute, right of setoff,
               counterclaim or defense exists with respect to all or any part of
               the Installment Collateral, and (iii) this Agreement creates a
               valid security interest in the Installment Collateral, securing
               the payment of the Outstanding Debt.

          3.   AspenTech will collect, in the ordinary course of business, at
               its own expense, all amounts due or to become due under each of
               the Installment Collateral. In the event that AspenTech fails to
               repay the Outstanding Debt in accordance with the schedule set
               forth in the License Fee Agreement, as amended, then all proceeds
               collected with respect to the Installment Collateral shall be
               paid to Accenture to satisfy the portion of the Outstanding Debt
               then due.

          4.   After February 1, 2003, in the event that the aggregate amounts
               outstanding and owed to AspenTech pursuant to the Installment
               Collateral is less than an amount equal to twice the amount of
               the Outstanding Debt, AspenTech shall grant to Accenture, on a
               first priority basis, a lien and security interest in additional
               installment receivables (the "Additional Collateral") in such
               amounts so that the aggregate amounts outstanding and owed to
               AspenTech pursuant to the Installment Collateral and such
               Additional Collateral are equal to an amount equal to twice the
               Outstanding Debt. AspenTech and Accenture shall mutually agree on
               those certain installment receivables that shall constitute
               Additional Collateral upon which AspenTech will grant a lien and
               security interest to Accenture.

          5.   Notwithstanding anything in this Agreement to the contrary,
               AspenTech expressly agrees that it shall remain liable under each
               of the contracts and agreements in the Installment Collateral and
               that it shall perform, in all material respects, all of its
               duties and obligations thereunder, all in accordance with and
               pursuant to the terms and provisions of each such contract or
               agreement. Accenture shall not have any obligation or liability
               under any contract or agreement in the Installment Collateral by
               reason of or arising out of this Agreement or the granting to
               Accenture of a lien therein or the receipt by Accenture of any
               payment relating to the Installment Collateral.

          6.   Accenture hereby releases its security interest in the Original
               Collateral and authorizes AspenTech's filing of Uniform
               Commercial Code ("UCC") termination statements to evidence such
               termination and release of its security interest in the Original
               Collateral.

          7.   Accenture agrees that it shall from time to time, upon reasonable
               request by AspenTech, (a) release its security interest in that
               portion of

<PAGE>

               the Installment Collateral and Additional Collateral that is in
               excess of twice the amount of the Outstanding Debt and (b)
               authorize AspenTech to file UCC termination statements to
               evidence such termination and release of Accenture's security
               interest in such excess portion of the Installment Collateral and
               Additional Collateral.

          8.   For so long as the Outstanding Debt remains outstanding,
               Accenture shall have the right, upon default by AspenTech of any
               of the material provisions of the Amended Agreements and the
               continuance of such default, to enforce the provisions of this
               Agreement and exercise remedies hereunder in such a manner as it
               may determine reasonable, including, without limitation, the
               rights to take possession, sell or otherwise dispose of the
               Installment Collateral or Additional Collateral, to incur other
               expenses with respect to such possession, sale or disposition and
               to exercise all rights and remedies as a secured lender under the
               Uniform Commercial Code of any applicable jurisdiction.

          9.   From time to time, upon the reasonable request of Accenture,
               AspenTech shall promptly execute and deliver any and all such
               further instruments and documents and take such further action as
               Accenture may reasonably deem necessary or desirable to obtain
               the full benefits of this Agreement, including, without
               limitation, facilitating the filing of UCC-1 Financing Statements
               in all applicable jurisdictions.

          10.  This Agreement shall terminate upon the full and final payment of
               the Outstanding Debt in accordance with the terms set forth in
               the License Fee Agreement, as amended.

          11.  No failure on the part of any of Accenture to exercise, and no
               delay in exercising any right hereunder, shall operate as a
               waiver thereof; nor shall any single or partial exercise of any
               such right preclude any other or further exercise thereof or the
               exercise of any other right. The wavier by Accenture of any
               breach of any provision of this Agreement or warranty or
               representation herein set forth will not be construed as a waiver
               of any subsequent breach. The failure to exercise any right
               hereunder by Accenture will not operate as a waiver of such
               right. All rights and remedies herein provided are cumulative.
               This Agreement may not be altered or amended except by a writing
               signed by all the parties hereto. This Agreement binds AspenTech,
               its successors and assigns, and inures to the benefit of
               Accenture, its successors and assigns."

     2.   AspenTech acknowledges and confirms that it shall pay to Accenture on
          February 1, 2003 the amounts which would otherwise be due to Accenture
          on February 28, 2003 pursuant to the terms of the License Fee
          Agreement, as amended. AspenTech further acknowledges and confirms
          that, prior to April 1, 2003, it shall pay to Accenture all amounts
          due on or before March 31, 2003 pursuant to the Amended Agreements.

     3.   This Amendment No.1 may be executed in counterparts, each of which so
          executed shall be deemed an original and both of which taken together
          shall constitute one and the same Agreement. In the event that a
          signature is executed and delivered by facsimile transmission, such
          signature shall create a binding obligation of the party on whose
          behalf such signature is executed with the same force and effect as if
          such facsimile signature were the original thereof.

IN WITNESS WHEREOF, the undersigned have each executed this Amendment No. 1 as
of the date first set forth above.

ACCENTURE LLP                                     ASPEN TECHNOLOGY, INC.

By: /s/ David A. Crow                             By: /s/ Lisa W. Zappala
    -----------------------------                     -------------------------
    Name: David A. Crow                               Lisa W. Zappala
    Title: Partner                                    Senior Vice President and
           ----------------------                     Chief Financial Officer

<PAGE>

                                   SCHEDULE A

DEBTOR: ASPEN TECHNOLOGY, INC.
SECURED PARTY: ACCENTURE LLP

<TABLE>
<CAPTION>
         CUSTOMER#              COUNTRY                     INVOICE                TYPE                 DUE DATE
         <S>                    <C>                         <C>                   <C>                   <C>
             3852               China                        124286               License               05/31/03
             3852               China                        124286               License               09/30/03
             3852               China                        124286               License               05/31/04
             3852               China                        124286               License               09/30/04
             3852               China                        124286               License               05/31/05

             1211               Japan                        122005               License               10/31/03
             1211               Japan                        122005               License               10/31/04
             1211               Japan                        122005               License               10/31/05

             1211               Japan                        123647               License               04/30/03
             1211               Japan                        123647               License               07/31/03
             1211               Japan                        123647               License               04/30/04
             1211               Japan                        123647               License               07/31/04
             1211               Japan                        123647               License               04/30/05
             1211               Japan                        123647               License               07/31/05
             1211               Japan                        123647               License               04/30/06
             1211               Japan                        123647               License               07/31/06
             1211               Japan                        123647               License               04/30/07

             1045           United Kingdom                   112488               License               07/01/03
             1045           United Kingdom                   112488               License               07/01/04

             1045           United Kingdom                   113626               License               10/01/03
             1045           United Kingdom                   113626               License               10/01/04

             1095            United States                   115683               License               04/01/03
             1095            United States                   115683               License               04/01/04
             1095            United States                   115683               License               04/01/05

             3928            United States                   124220               License               04/15/03
             3928            United States                   124220               License               06/15/03

             6365               France                       122549               License               04/01/03
             6365               France                       122549               License               04/01/04
             6365               France                       122549               License               04/01/05
             6365               France                       122549               License               04/01/06
             6365               France                       122549               License               04/01/07

             7710               Germany                      122618               License               01/01/04
             7710               Germany                      122618               License               01/01/05
             7710               Germany                      122618               License               01/01/06
             7710               Germany                      122618               License               01/01/07

<PAGE>

                                   SCHEDULE A

DEBTOR: ASPEN TECHNOLOGY, INC.
SECURED PARTY: ACCENTURE LLP

<CAPTION>
         CUSTOMER#              COUNTRY                     INVOICE                TYPE                 DUE DATE
         <S>                    <C>                         <C>                   <C>                   <C>
             9677               Germany                      122653               License               01/01/04
             9677               Germany                      122653               License               01/01/05
             9677               Germany                      122653               License               01/01/06
             9677               Germany                      122653               License               01/01/07

            10851               Belgium                      124278               License               10/01/03
            10851               Belgium                      124278               License               10/01/04
            10851               Belgium                      124278               License               10/01/05
            10851               Belgium                      124278               License               10/01/06
            10851               Belgium                      124278               License               10/01/07

             2587             Netherlands                    124277               License               10/01/03
             2587             Netherlands                    124277               License               10/01/04
             2587             Netherlands                    124277               License               10/01/05
             2587             Netherlands                    124277               License               10/01/06
             2587             Netherlands                    124277               License               10/01/07
</TABLE>

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