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








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