Corrupted user account

[John Ward]

One of my user accounts appears to be corrupted. The user
name is no longer listed under users, but when I try to
add it again it says it already exists.

 

[JeffO]

Right-click the "My Computer" icon and go to "User
Profiles". (Warning, this will delete ALL the user files!
So back up all data in your Favorites, My Documents, etc.)
Choose the old profile, if it appears, and click the
delete button.
If all you see are weird ASCII boxes and symbols, delete
them. They're trashed profiles.
If you still can't get this done, try renaming the profile
folder in C:\Documents and Settings. Then try adding the
new one again.

 

[John Ward]

I have deleted the profile and no files remain for it.
However, when I try to recreate the user I get the message:

'The user <username> could not be added because this user
already has permission to use this computer'.