"Stop 0xD1 messages can occur after installing faulty drivers or system services. If a driver is listed by name, disable, remove, or roll back that driver to confirm that this resolves the error. If so, contact the manufacturer about a possible update. Using updated software is especially important for backup programs, multimedia applications, antivirus scanners, DVD playback, and CD mastering tools."
- microsoft

The common fixes are SYSTEM RESTORE (use SAFE MODE), LAST KNOWN GOOD BOOT and installing the OS again.

Bob