How to delete and recreate the user profile on the local computer (Vista)
1. restart the computer and logon with an administrator account.
2. Rename (or delete) the existing user profile folder: "c:\users\xxxxx"
3.Open Registry Editor (regedit.exe)
4. First, export to backup the registry key: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
5. Then, expand the ProfileList and delete the key which the Data of ProfileImagePath is “C:\users\xxxxxx”
6. Log off and try to logon with the problematic account.