According to a thread from a while back, the culprit behind a certain KERNEL32.DLL crash in Vista was identified, but a true correction was deemed untenable. In that same thread, methods were discovered for forcing RetroArch 64-bit to run successfully in Vista regardless, by making use of certain DLLs found in the last non-buggy RetroArch, 1.3.0.
That method doesn’t work with today’s RetroArch.
In point of fact, two of the replacement DLLs (avcodec-56.dll, avformat.56.dll) no longer even share the same name, and the third (libx265.dll) is only half the size of the current libx.265.dll and RetroArch, understandably, complains about missing functions when the replacement is made regardless.