If your registry is still in tact, there are tools that will tell you what
key you used to install Office XP and Windows XP. I downloaded one that is
called Magical Jelly Bean Keyfinder. Sorry, but I forgot where I found it.
It looks in your registry for the encrypted key and decodes it for you. I
don't know if it is MS approved, but I don't see why not since why not since
part of MS's OEM agreement is that you have to put your OEM tags with the
key number on the outside of the PC for all the world to see anyway.
If you didn't format your drive, Google for the keyfinder, write it down,
and reinstall. Watch out for situations where you have multiple versions of
XP or office 2003 installed. I have a few computers that have just Office
Basic and I have installed the Access 2003 Runtime engine to run some Access
stuff and they key finder shows more than one key and they both say "Office"
Don't get a Key Generator because that is illegal and the keys are not some
randomly created keys that are generated by a top secret algorithm. They
are a list of keys that everyone and their grandmother has posted and they
have already been black listed by MS so don't even bother.