MinGW is compatible, yes

Yes - that's what I was unsure about. On first reading I thought you were saying that Visual Studio 6 must be used (which would be incorrect). You weren't saying that (you were correct :-)

As regards the other Visual Studio compilers, my hunch is that VC 7.0 (at least) would build Win32::OLE for ActivePerl, but I haven't checked.

Cheers,
Rob