This is a rather nasty error that could be caused by just about anything, including busted audio drivers, incompatible video drivers, bad or corrupt hard disk, and faulty hardware such as bad RAM. If the crash is associated with plugging in some hardware, use device manager to remove the device drivers. Use msconfig to disable any services associated with the hardware and any other startup services that are not essential.
Visit the manufacturer’s website and try to locate up to date drivers. Most often, x50 is associated with dud RAM. That includes main memory, video and CPU cache memory. If you have more than one stick of RAM, start ripping the sticks out one at a time. If you only have one stick, you will need to find someone who can help you out with a spare stick that fits your machine.
If all else fails....desprate measures you can Disable all BIOS caching and speed-up options. Disable power management. If you are overclocking, don't.
Antivirus software can cause this error. Disable any antivirus software you have. Run Chkdsk /f to check for disk errors because corrupt disk volumes can cause this, too. Check Event Viewer to see if there are any additional errors or warnings that might provide a clue.
if nothng else, found this at microsoft>
hope it helps
link