error-checking / optimization

[Joe Hetz]

We are performing our end of school year maintenance on
our Windows XP Pro PC's (Disk Cleanup - Error Checking -
Optimization). After running the error-checking (Check
Disk) at reboot because fix errors automatically has been
chosen we are then sent to a black screen. We have to
restart and select the last known good config option. Any
idea why this happens?

Also will the Optimization program run if error-checking
is not done and there are disk errors that would have been
found?