Ok, windows paths with forward slashes work, I can now start the installed guile.exe without setting environment variables. Always nice when the inconsistent formats are the working ones :)
The remaining issue is that it hangs itself after printing that it is loading q.scm. Not sure how exactly to appreoach this problem. I guess I'm gonna put a lot more debug output into the the various load functions. Or I'm gonna make debug builds and fire up gdb on windows. Or maybe you have an idea.