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                      AMENDED AND RESTATED PROMISSORY NOTE

$17,410.20                                            September 9, 1999
                                                      Lexington, Massachusetts

                  FOR VALUE RECEIVED, Kenneth Welch (the "BORROWER"), hereby
promises to pay to the order of MOLDFLOW CORPORATION (the "COMPANY"), the
principal amount of $17,410.20, together with simple interest from the date
hereof on the unpaid principal balance hereof, which shall accrue at a rate
per annum equal to five and 77/100 percent (5.77%). Accrued interest on the
principal amount hereunder that may be outstanding from time to time shall be
due and payable, at the Borrower's election, (i) quarterly in arrears
beginning June 30, 1998 and on the last business day of each successive
quarter thereafter, or (ii) in full on June 30, 2003 (the "Maturity Date").
All unpaid principal and interest hereunder shall be due and payable on June
30, 2003. Interest shall be computed on the basis of a 360-day year and a
30-day month. The unpaid principal balance and all accrued interest on this
Promissory Note at any time shall be determined from the records of the
Company, which shall constitute presumptive evidence of such amounts.

                  This Promissory Note amends and restates the terms and
conditions of the obligations of the Borrower under the Promissory Note dated
as of July 1, 1998 (the "Original Note") from the Borrower to the Company.
Nothing contained in this Promissory Note shall be deemed to create or
represent the issuance of new indebtedness or the exchange by the Borrower of
the Original Note for a new Promissory Note. The indebtedness set forth in
the Original Note continues in full force and effect in this Promissory Note.
This Promissory Note may be voluntarily prepaid in whole or in part at any
time without premium or penalty, but together with interest on the principal
amount so prepaid accrued to the date of prepayment.

                  Payments of both principal and interest hereon shall be
made in immediately available funds at the office of the Company, at 91
Hartwell Avenue, Lexington, Massachusetts, or at such other place as the
holder hereof shall designate to the Borrower in writing, in lawful money of
the United States of America.

                  Except to the extent otherwise required by the context of
this Promissory Note, the word "Company" wherever used herein shall mean and
include the holder of this Promissory Note originally issued to Moldflow
Corporation.

                  This Promissory Note shall be deemed to be a contract under
the laws of the Commonwealth of Massachusetts, and for all purposes shall be
governed by the construed in accordance with the laws of said Commonwealth.

                  This Promissory Note shall be non-recourse to the Borrower,
except as to 40% of the Borrower's total obligations, including principal and
interest, outstanding from time to time under this Promissory Note, for which
the Company shall have full recourse to the Borrower.


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Further, the 40% obligation subject to such full recourse shall by specific
attribution include first any unpaid interest obligation of the Borrower, to
the extent any such interest does not exceed 40% of the total obligation.

                  The Borrower waives presentment, demand, notice, protest
and all other demands and notices in connection with the delivery,
acceptance, performance, default and enforcement of this Promissory Note.

                                       By: /s/ Kenneth Welch
                                           ------------------------------
                                               Kenneth Welch

                                       Address: 11 Hastings Road
                                                Weston, MA 02194