You get GACUTIL by installing the .NET SDK. It is not installed by default.
http://www.microsoft.com/downloads/details.aspx?FamilyID=9b3a2ca6-3647-4070-9f41-a333c6b9181d&displaylang=en
Follow the steps in the 6-02-04 post in the following thread:
http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=591348
If you still have problems reply back to the forum.
-Dan
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