After you have deleted or renamed a user profile in Windows 7 sometimes a new profile will not be created with the same user name. This is because there is a pointer in the registry that is pointing to a non existent profile and will have to be removed.
To do this back up you registry and then navigate to
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
Or search the registry for profilelist.
Locate the key and delete.
Adapted from Technet
