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                                                                   EXHIBIT 10.07

                                 AMENDMENT NO. 1
                                       TO
           AGREEMENT FOR EXCHANGE AND PURCHASE AND ESCROW INSTRUCTIONS


This AMENDMENT NO. 1 TO AGREEMENT FOR EXCHANGE AND PURCHASE AND ESCROW
INSTRUCTIONS ("Amendment No. 1") is made as of November 4, 1998 by and between
SYMANTEC CORPORATION, a Delaware corporation ("Symantec") and TST DEVELOPMENT,
L.L.C., a Delaware limited liability company ("TST") with reference to the
following:

A.      Symantec and TST are parties to that certain Agreement for Exchange and
        Purchase and Escrow Instructions dated as of September 22, 1998 (the
        "Agreement").

B.      The parties now desire to amend the Agreement to extend the end of the
        Feasibility Period.

C.      All capitalized terms used in this Amendment No. 1 shall have the same
        meaning as defined in the Agreement unless separately defined herein.

                                    AGREEMENT

1. Notwithstanding anything to the contrary in the Agreement the end of the
   Feasibility Period is hereby extended to 5:00 p.m. PST on November 20,
   1998.

2. This Amendment may be executed in one or more counterparts pursuant to the
   Agreement. 

3. Except as herein amended, the Agreement remains unchanged and in full
   force and effect.

IN WITNESS WHEREOF, the parties hereto have executed this Amendment No. 1 as of
November 4, 1998.


                                            
"SYMANTEC"                                     "TST"
SYMANTEC CORPORATION,                          TST DEVELOPMENT, L.L.C., a 
A Delaware corporation                         Delaware limited liability company
By: _/s/ Derek P. Witte________________        By: /s/ Andrew J. Nathan____________
Name: __Derek P. Witte_______________          Name: _Andrew J. Nathan__________
Its __Vice President, General Counsel &        Its__Vice_President____________
Secretary________________