I have five systems in the shop right now that will not boot to XP. Three are XP Home & 2 are XP Pro. All are valid legal copies. It boots to the black screen with the green status bar below, but then just shuts down and restarts. I've been able to fix a few through the recovery console (chkdsk), but not these other 5. Just wondering if this could be cause by the user not activating their copy? If so, how can I activate it without being able to boot? Thank in advance for any help.

PS--I can't boot in safe mode either.