I have read some posts regarding the Machine Check Event reported is a fatal memory hierarchy error (WMIxWDM) errors. There have been no resolution except for Microsoft telling you to upgrade your PC to the latest BIOS...which was done and didn't work. I have a gigabyte K8U 939 MOBO with the AMD x2 3800 Dual Processor. A GeForce 5500 Dual Video card and 2 (1 gig) CORSAIR Chips - Running Dual DDR Enabled. Any idea why these Events 120 and 123 keep coming up? The system is a dual boot system and these errors only appear running XP Pro x64 not XP Pro. And yes, I have updated the AMD drivers, tested and replaced the memory as well. Any help would be appreciated. Thanks Mike