|Hi all, first of all, keeping to XP wouldn't be the greatest idea if you want to play the latest games, as most new PC games are "make for Windows", as in Vista.|
Though, if you waited for Win 7, that would probably be better, since you'll only have to wait 'till October, and most things people didn't like in Vista will (hopefully) be fixed.
Now, for the specs...
LIke these guys are saying, your specs are fine, just upgrade the RAM, since most games today require at least 1GB.
Although, if you're running Vista, it's best to have at least 2GB of RAM (DDR2 or DDR3 doesn't matter), since the OS takes up a whole GB just to run.
EDIT: Does the game say "Games For Windows" at the top of the case? If so, you MUST have Vista. Microsoft made all game devs. make their games for all their newest operating systems (Vista, and now, when it comes out, Windows 7).
I know that's a bit disheartening, since some still view XP as a reliable OS, but it's just a cruel way to make sure you upgrade and go with the newest-gen flow.
I hope Windows 7 is better than Vista.
The Ubuntu project sure is.