What happens when you go to Safe Mode:
Start your computer.
Tap the F8 key before Windows starts, to bring up the Windows Advanced Options menu
Use the arrow keys to select Safe Mode
What Users does it show there?
Can you do the following:
Press the 'Windows key' and 'R' simultaneously.
In the Run box, type (or copy/paste) the following in the Open area:
In the upper section of the User's tab, un-check: 'Users must enter a user name and password to use this computer'.
Post back on how it goes...
Retired - Doin' Dis, Dat, and slapping malware.