Are you sure that the 32-bit version doesn't just run on 64-bit Windows, without modification? Most things do.
Failing that, have you actually tried just compiling it for 64-bit? A brief scan of a few Google Groups etc where people asked this same question suggests that that may be exactly the solution to this. I think you're probably overestimating the difference between 32-bit and 64-bit Windows (at least as far as compiling a native application goes).
