weird error. Try this: Go to start > run > regedit.exe > that will bring up the registry,which looks sort of like the explorer window > expand the following ( \ marks mean click the plus sign next to the file)
HKEY_CURRENT_USERS \ Software \ Microsoft \ Windows NT \ CurrentVersion \ Winlogon
click on winlog, see if there is a file called 'shell' in the right hand pane....let me know if it's there or not.....
be CAREFUL in the registry. Do NOT delete anything, or modify anything unless explicity instructed to; you mess something up in there, bad things can happen in a hurry.
thanks,
v