[hrydgard]

Not the case. Actual thunking is only done when calling into the kernel, you can't load a 32-bit DLL into a 64-bit process or vice versa.

[fredoralive]

I think GP is thinking more of how Windows 9x did 16 and 32 bit, which was full of funky thunking and only really had one set of libraries AFAIK (awaiting inevitable correction).