It might be possible but first you'd have to find out what CPUs exactly are in both PCs, and what motherboard and socket.
If they are the same socket - and both motherboards support the other CPU then it should be possible.
If you are unsure about how to find out what motherboard(s) you have try Everest Home Edition (
http://www.lavalys.com/products/over...pid=1&lang=en).