ReProfiler for Windows can fix your corrupt or unavailable user profile
Highlight a user account, then click the properties button to see what details are attached to it. ReProfiler will display the user's name, domain, SID, and profile path. It'll also tell you if that account is currently logged on and advise you to log it off prior to attempt to performing any other actions.
Once it's logged off, you can use detach to disconnect a profile from a data folder or assign to re-attach. If you're getting a message when you log in that Windows was unable to load your profile due to some form of error, ReProfiler's assign button could very well provide an automated fix -- just make sure you log in as a different user first.
ReProfiler runs on Windows XP, Vista, and 7. It's a great tool to keep on a network share or your USB flash drive if you're an admin or technician.