I just upgraded my athlon 64 4000 to the x2 4800 cpu. I didn't format I just installed the new cpu and installed the amd dual core driver, dual core optimizer and the microsoft fix. In the device manager it shows 2 cpu's. Is their anything else I need to check to make sure that the cpu is working the correct way? Did most of you format before upgrading the cpu? Windows seems to be running fine with no problems yet.