Although it is a bit of a cop out, re-installation of XP could be considered. I hope he has backups of his personal data! If not, and you can get the current version of XP working well enough, then it may be possible to copy his "my documents" folder into a folder with another name on the hard disc. When it re-installs, windoze will delete the existing "my documents" folder but should leave any other one alone.
P.P.