You may be getting a BSOD (Blue Screen of Death) error that you are not seeing, because XP automatically restarts. To turn off the automatic restart: Click Start, right click My Computer, click Properties, Click on the Advanced Tab, click Settings under Startup and Recovery, and under the System Failure options uncheck Automatically Restart. This happened on my PC and a Microsoft Engineer told me how to turn off the automatic restart. After doing this, I was able to see the error message that pointed me to the driver that was keeping the system from shuting down.