Use Driver Cleaner to remove all those things again.
Check this link: Previous Radeon Drivers
That's the 8.8 for XP Pro. Just download the Drivers and not the CCC. Erase all the other things you downloaded just to be sure before downloading this one. After the drivers are installed, try some games. They should work and all.
Anyway, I'm kinda interested in finding wich exact Service Pack you have on your Windows install... If you have "Windows Professional SP2" you should be good, but if you have SP1 or even lesser, no driver is going to work fine for you IMO. Can't assure that, but everything seems to point that.
EDIT: Little error in typo.