I've just listened to episode 6 of StackOverflow podcast, and I just wonder, is there a free and good enough implementation of Mac Spaces for Windows?
A:
No there isn't, at least not for XP. It's hard because xp wasn't designed with that in mind, while Mac and Linux handle it beautifully.
The best one for XP that I have found is VirtualWin, which just works by hiding windows. It's hacky, but at least it gets the main idea down. I think if you've got an accelerated desktop like vista, VDM might be worth a look. But since I don't have vista, I can't be sure.