if your just going to use the computer for internet, go ahead, use XP.
But...if you want to play games, try to use a different O.S. as XP will hog up all the memory, unless you change the performance settings.
Windows 2000/98 are still going to work fine, they still get updates, and game playing will run alot better.
If you are going to use XP, upgrade to service pack 2.
It has a pop-up blocker as well as the firewall.