BSOD while playing NFS the run and general usage

i have been encountered with BSOD while playing NFS the run and general usage usually i got an BSOD with atikmpag.sys error while playing the game and randomly using the computer is bad pool header i have uninstalled the driver used driversweeper in safe mood to clean the files and reinstalled the latest ATI catalyst 12.6 however the same problem persists i have currently installed the previous version of catalyst 11.7 and the same problem persists.

i would be thank ful if anyone can help me out

PS and my PC works fine in windows xp professional i have never encountered such kind of errors plus i have ran memtest which has detected no errors

anyone?