If other people can logon sucessfully, I would look at your profile being the problem.
Personally, I would just create a new profile and copy over the important stuff (like my music and my pictures). But you can recreate your profile if you want the same username.
Log on as administrator and locate your files. c:\documents and settings\"username"\my documents. (P.S. this is for Win XP, but im sure its almost the same in Vista.) Then just copy it to the c drive for now, then create a new profile under control panel, user accounts. Then copy your stuff back.
Like i said, I cannot remember where the files are in Vista, but it should be very easy to locate.
Hope it helps..