When Windows loads, press SPACE BAR when the "Load Last Known Good" message appears.
Complete a parallel installation and restore the registry files from a tape backup. To do so:
Reinstall Windows into a separate directory
Restore the registry hives found in the %SYSTEMROOT%\System32\Config subdirectory.
If you do not have a tape backup, the backup of network servers and production workstations should be included as a critical part of running any production system.
NOTE: If Windows is stored on a FAT partition, you can restore the files using another computer and by copying the registry hive files into the directory above.