Ahh OK, wasnt sure what you meant there. I would say try the login as THE ADMIN first then if the same error you may need to do a clean repair install (Which will mean you will have to go get all your drivers again as well) Which is best to actually do After the windows updates, sometimes drivers installed cause Update installation errors.
You could also just install all updates first EXCEPT SP3 then download SP3 and install manually
(*NOTE* You must have either Windows XP Service Pack 1a or Windows XP Service Pack 2 installed in order to install Windows XP Service Pack 3.) >>>>
Download details: Windows XP Service Pack 3 Network Installation Package for IT Professionals and Developers
Which may be the better way to go about doing it on a clean install