Although Mini vMac wx86 (without assembly code) will build in an x64 compiler chain, the Windows x64 only became an official supported architecture in Mini vMac 3.2.3 beta.
My x64 builds using Visual Studio 2008 SP1:
http://www.mediafire.com/?bx3v2w1vwvxu8so
Mini vMac 3.2.3 beta Windows x64 build
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