Have you checked out what's happening in the User Accounts control panel? Do the accounts still have names there?
If you haven't installed anything or changed any settings, it might be the work of spyware and viruses. Run a scan with some spyware and virus scanners. Also, try running System Restore back to a date when you had user names displayed.
alc6379
Cookie... That's it
2,820 posts since Dec 2003
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Try hitting "ctrl-alt-del" and then hitting del again. It should take you to a login screen, where you might be able to type in a user name.
Have you tried logging into safe mode yet? You might still have access to the Administrator account.
alc6379
Cookie... That's it
2,820 posts since Dec 2003
Reputation Points: 186
Solved Threads: 147