This usually happens when the registry portion for that
user (ntuser.dat) is corrupted.
Try logging into a different account.
Copy the files from the Administrator account in
C:\WINNT\Profiles\Administrator.%COMPUTERNAME%
Delete to contents of that folder.
Logon as Administrator to recreate th profile.
Copy any files needed from the backup copy except
NTUSER.DAT and NTUSER.DAT.LOG.