Aha. Kind of a bummer. With LE software, the iLok does not help and you/he needs that authorization code, so a fresh start is pretty much not possible. I would try to download that same version and drop it on the desktop. It might be possible to run the installer and select a "Repair" option(which might install the driver you are missing)
Given all this, and that he knows very little about computers, it might be 100 times easier to choose a different course
Any XP machine is going to be really out-dated and no current computer will run the old PT software. He may be happier with a new(er) PC, a modest interface and some modern DAW, be it Pro Tools, Reaper, Studio One, etc