Is there a way of telling which version of MSWIN32 is being used for a perl script?

See Win32::GetOSVersion() &| Win32::GetOSName(). It comes with AS Perl's. Not sure about other Win32 perl variants.

I have found that notepad is under a different direcory on Vista to W2K or XP. I can check to see if the file is in a number of places

Wherever it is located, it will be in the (standard) path, so why not just let the shell find it?