Have you tried scanning the disk for bad sectors?
(in my computer, right click on C drive, select properties, Tools, error checking and tick check for bad sectors <-- might have to adapt that for XP/these are for Win 2000)
That would give you pretty good idea as to the physical state of the HD.
And if you're going to buy one I'd go down the SATA route - your motherboard doesn't seem to support it but you can a PCI adapter card for £20
Dabs.com and an 80GB SATA for £44 (again
dabs.com ) - this will give some extra speed - wish I'd done it when my HD broken a few weeks ago...
My 2p anyway..