AMDKMDAP has stopped working

Dell xps420 3gig mem, ati 2400 pro 128mb, vista64 ultimate. When ever it feels like it my computer freezes and sometimes even gives me the blue screen of death. surfing the web or watching a movie with media center. I have tried

1 unstall driver, use driver sweeper to clean, reinstall the driver from dell, ati, and asus.

2 Check memory to see if one or more sticks are bad

3 chkdsk hd to see if there were bad sectors.

4 Read everywhere to see if another problem like mine exsits cant find one

The problem started about 2 months ago, I have not installed any software or hardware nor has windows updated with in a week or so before it started, it has sence but the problem still is here does anyone have any suggestions? could it be the card it self?  can you  help me?