The installer *is* correct, just its message isn't that helpful - you simply can't mix and match 32 and 64bit binaries. I'm not sure about ctypes, but there will never be a pywin32 64bit Python 2.5 build - only 2.6 and later. It is possible that Python 2.5.4 has ctypes enabled though - that might be worth checking. Alternatively, just install the 32bit version of Python 2.5 - it works just fine on a 64bit OS.
The installer *is* correct, just its message isn't that helpful - you simply can't mix and match 32 and 64bit binaries. I'm not sure about ctypes, but there will never be a pywin32 64bit Python 2.5 build - only 2.6 and later. It is possible that Python 2.5.4 has ctypes enabled though - that might be worth checking. Alternatively, just install the 32bit version of Python 2.5 - it works just fine on a 64bit OS.