I'd like to propose we delete Lib/Distutils/command/wininst-9.0.exe, and enable the building of that project by default in the standard build process (and I'll setup the x64 build of the executable similarly).
There are two issues here: a) how does the binary get into the release tarball? You might argue that it doesn't have to, as it is sufficient when it is included in the Windows installer, however, as currently implemented, bdist_wininst also runs on Unix, and people use it that way. b) IIRC, upx was used to compress these executables. I don't think the the current build process covers this, yet (but then, the current binaries might not be compressed with upx anymore, either - not sure whether that would be a bug). Of course, upx would probably not currently apply to Win64-amd64.
As another alternative to providing a separate AMD64 binary, you could also try to make the existing binary work properly on Win64, and tell it with a config flag whether to look for Win32 or Win64 (or either) on the target system.
Regards, Martin