£130 to rebuild two PC's and transfer a load of files over between them isn't actually that bad, sorry to say. There's a fair old bit of work involved. Do you have restore CD's for both machines? If not they will have to built from scratch which involves loading XP, THEN the drivers for the various video cards, sound cards, network cards, etc, any service packs plus updates. Then you get into software. Word, excel, antivirus, firewall, etc. I assume you have all the CD's required?
Typically speaking, building a PC from scratch takes at least 2 - 3 hours (XP takes over an hour by itself) assuming you have all the software to hand. If you have to start searching for drivers, etc it takes even longer.
And IF (big IF), it turns out that your XP problem is not causing by the software dying, someone's gonna have to start troubleshooting. Could be dodgy hard drive, dodgy RAM, badly seated RAM or video card, dodgy power supply, or (god forbid) motherboard going bad. You get the idea.
A shop would be able to sort all this out, which also means you'd have some support if it goes wrong later. They could also back up all your Dads files to a couple of CD's (or DVD's if its a lot of info). That way you have the "sentimental things" doubly saved.
You could look in the back of your local paper for freelancing techies, but they usually bill out at £25-£30 per hour (anyone who charges less than that is not worth trusting with your stuff). But £30 per hour x the 4 hours MINIMUM build time i mentioned above is £120.
Just a few thoughts to throw at you...
