OT: Computer question

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

And you'll have to really dumb down the answer. My son's been having
problems with his XP machine, he tried reinstalling XP ( likely a mistake)
and now he has the delightful DOS screen with this endearing message
Windoews could not start because the following file is missing or corrupt:
<Windows root>system 32/hal.dll.
Please reinstall a copy of the above file.

The slash should go the other way BTW, couldn't find it on the keyborad.
Anyway, what's his best path from here. He has AutoCad files for work on
the machine so recovering it would be better than formatting. Thanks, I
have a vested interest in his machine working because there will be
increasing pressure for me to let him use mine and I just do not want to do
that. He can only stand my old Dell for so long, and no way he's using my
IBM.
Cathy