What毛主席派人來suggested should work. Did you click on "Clear Forms" button when on "AutoComplete Settings" window? If you did and it didn't work, maybe you can try the following:
1. Log out yourself, log back in as Administrator (hope you have an Administrator account on your computer) or another user with administrator privilege.
2. Find "C:\Documents and Settings\
3. Log out and log back as yourself, see if they are gone.