I recently had to fix a Desktop computer, running Vista. It would boot up to the log-in screen which seemed oddly different. There was no picture, just an empty frame with a empty space under for a username and a empty space for a password.
I fixed a laptop with a similar log-in problem by erasing the password. But this time it didn't work. So I had to find another way. Not surprisingly all the built in utilities for Vista didn't work. I'm referring to the start up repair options. - www.bleepingcomputer.com/tutorials/tutorial148.html
Some online checking suggested it to be a corrupt Registration Database. I found the instructions for doing it through the recovery console but decided to do it slightly different way.
I had already downloaded and burned of a copy of Hiren's Boot CD - http://www.hirensbootcd.org/download/
The download link is at the very bottom of the page.
Boot of Hiren's CD.
It has a Mini-XP boot option that gives you a Windows Xp enviroment to work with. The one utility I was interested in was the Windows Explorer. I needed to be able to access the files on the hard-drive.
Using Explorer I navigated to the c:\Windows\system32\config. Inside is a sub-folder called Regback.
The path is c:\Windows\system32\config\RegBack
Back to the config folder. Look for the following five files:
There are a number of similar named files in this folder, these do not have any extensions.
Its recommended that you first rename these five files, don't matter what. My choice was; default.old, sam.old, security.old, software.old, system.old.
Then go back to the Regback folder and find the same five files. Copy all 5 over to the config folder, as is. That's it. Now take out the CD and restart the computer.
When the computer restarted after this I was taken to a menu with two option; Start Windows Normally and Repair Windows. To be sure I chose Repair Windows. The system rebooted almost instantly, and booted up normally after.