Athlon64 2800 Socket754

Hi everybody.
An old fellow over the street from me was having problems with his computer
and I offered to help. To keep it short the problem is his CPU. I said to
contact the company that sold the computer to him and he said they have gone
belly up and are no longer around. Not a problem I thought so I said to go
straight to AMD and as long as he had the purchase reciept he should get
warranty. The catch is that they can't seem to find the reciept for the
computer which was bought around June 2005. He does have the box that the
CPU and heatsink and fan came in as the seller told him to keep the boxes
that all the parts come in just in case of warranty. I don't really want to
become involved between him and AMD so I thought I would ask if anyone here
has had a similar problem with an AMD CPU.
I did say to just go out and buy a Sempron to get him going again but he
says that as a pensioner he can't see his way clear at this time to fork out
another $100 or so.
Anybody got any ideas please? Our location is the Gold Coast, Australia.