I choose Windows, simply because i'm most familiar with it's aspects, good compatibility, easy to use and pretty efficient in my opinion. I've tried a few distributions of Linux, such as Fedora Core 4 and Ubuntu Breezy Badger, but i still haven't been able to get used to it, it's confusing for me and i guess i just don't know here to start.
Saying all this, Windows XP definately gets my vote.
Saying all this, Windows XP definately gets my vote.