This is a Vista User Profile Service problem and there are certainly a lot of posts across the Internet about this difficulty. It seems to occur when there are two or more user Profiles set up. But there are a small number of single users who also report the same problem. It does not seem to matter whether the users are 'administrators' or 'standard' users.
It seems likely that the affected users Profile has somehow been damaged and is frozen. As a result, Vista has changed the Profile's extension to .bak - a backup file. This makes the user Profile unavailable and so produces the message:
The User Profile Service failed the logon.
User Profile cannot be loaded.
At QBS PC Help we had to find an answer to this problem as we had a Dell Laptop, running Vista, to repair. This exhibited the same User Profile Service problem. Thankfully the Laptop had two user accounts set up, one administrator and one standard user. It was the standard users account that had frozen.
A few searches in Google led us to the Vista Update forum which has a post on this topic.
Of course if you are the only user of your PC you've probably got only one user profile set up and you are no doubt the administrator. So if this account is frozen your only option is to try and repair Windows Vista.
Turn on your computer, and press and hold F8. You will see on the screen that appears the option to " Repair Your Computer". Select this and hit Enter. (use your own administrator user name and password).
On the next screen you will see the first Category "Startup Repair" and the second "System Restore". Click on Startup Repair. When this finishes restart your computer.
If the Startup Repair doesn't work try the second option - System Restore. Again when its done, restart your computer.
Hopefully, your user account is now working again.
If you have two or more user accounts set up then the following solution works. We fixed the Dell Laptop by taking these steps.
First, you need to log on with an administrators account.
Now go to Start and in the Search Box type regedit. Get past the nagging security box and wait till regedit opens.
Now go to:
Go through the listed Profiles to find the damaged Profile. The key to the damaged profile should have a .bak appended to it.
There should also be another identical key except for the .bak extension. Rename this other key to something else (e.g. one number above the highest number).
Also rename your damaged Profile by removing the .bak extension. Now change the State property of this Profile (listed in the right hand window) from 1 to 0.
Restart your PC and try logging on with your Profile. It should now work.
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