Pop Ups

Have a fairly new system running XP Pro. Have AVG anti virus, Spybot search and destroy and ad-aware. With all this i still have annoying pop ups and when I do a search/google get directed to pages not requested….
I have run scans in safe mode and found objects and deleted them. I also turned off system restore before doing this but they still keep comming back. Help please? My next step is a complete reinstall of XP…

Thanks
Michael