What I did was replaced the 80 gig HDD with a
160 $75 and got a OEM copy of
XP Pro $135. then installed XP to the new HDD.
First you have to make sure you have all the drivers downloaded for your hardware and burn to CD.
Once I had the install completed with no issues.
I then took the 80 and installed it in an external HDD enclosure, repartitioned and formated it and now use it for storage.
Note: The reason I did it his way was if there was a problem, I still had the original drive in tact so I could reinstall.