There is a small possibility that doing an installation and choosing the "Repair Current Installation" may work.
Note that this is NOT the same as booting from installation CD and choosing the Repair option - boot from CD, choose Install THEN choose Repair Existing.
See
here.
He can also do an installation alongside the existing (assuming there is sufficient space) to avoid overwriting data - do this to recover data that has not been backed up, back up the data to CD or another PC or disk, then do a format and clean install.
SD