Thanks for the replies,
My reseller has no experience with that called Virtual PC running XP on Vista.
So I went for the XP downgrade and everything works fine.
I have certainly done that, more than once.
It's usefull when it comes to basic construction elements and 2D data.
Unfortunately, these 60+ housing projects are not cross-platform and on Mac all library parts are missing due to naming issues...that's why I need the .pla option on