If you wanted to delete a roaming user profile from a local computer on Windows XP machine you could simply open Documents and Settings and delete profile folder manually. User would get a new profile from a server next time he logs on.

If you try this approach on Windows 7 or Windows Vista machine, user whose profile was deleted, won’t be able to logon. Instead, he will get an error:
The User Profile Service failed the logon. User profile cannot be loaded

This happens because deleting profile folder in Windows Vista or Windows 7 manually doesn’t remove Security Identifier (SID) from the profile list in the registry. If entry is still there, Windows tries to load a profile from non exiting folder and fails with the above error.

To resolve the issue you need to remove SID from registry:

1. Logon as another administrative user
2. Open registry editor (Start > regedit)
3. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
4. Each profile will be represented by a long SID number starting S-1-5
   
   
5. Locate the SID representing the profile in question. To do this simply go inside of each SID and check ProfileImagePath values, which will show local profile path.
6. Right click on the SSID and click Delete

Proper way to remove user profile folder in Windows 7 and Windows Vista is:

1. Logon as another administrative user.
2. Open Computer > Properties > Advanced System Settings > User Profiles > Settings
3. Select user profile and click Delete