The User Profile Service failed the logon. User profile cannot be loaded - FIXED

I’ve seen this a couple of times now with Vista, and thankfully it’s a fairly straightforward fix:

Log on as another user with Administrative rights.

Start regedit and go to the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList

Here you’ll see a list of SIDs for each user profile, and you should find there are two with the same SID, however one ends with “.bak”.   You need to swap these around – essentially restoring the backup SID.

Once swapped – set both State and Refcount to 0 and then reboot. Fingers crossed, everything should be back to normal!

For a good step through of the process – take a look at this walkthrough.