It aint just the popups, what about all the 'xp phone home' stuff?........ .....nice to know that M$ get a record of anything you install, PLAY or BURN on your pc isn't it?..............and believe it or not there are still idiots out there using WMP8/9 ..............or the inbuilt burning software.
Or the fact that it 'borrows' about 20% of your internet bandwith, without asking?
Or as noted above virtually DEMANDS you get a Net Passport (so they can track you just that bit easier)..............
Or maybe the fact that a new install is WIDE OPEN and has ZERO security?...........
What you MUST do with EVERY new XP install is get those services under control....... get a good firewall..... (NEVER use the xp firewall, it only stops things coming IN, when its the stuff going OUT that you need to stop the most!) like Outpost, Sygate or Kerio and CONFIGURE it correctly.... use your firewall in conjunction with the Proxomitron (or similar) for added protection.
Then comes your AV..... then Adaware and Spybot.
Only at this point is your XP install ready for the big wide world...........
Changing your browser might be good idea too........
After that XP is pretty good (ish) imo.