You do not mention what OS your old and new PC's have.If they are both Windows 7 then it is now very easy to network the 2 PC's. If one is XP it can be very troublesome, I gave up on my XP Pc and installed Windows 7 on it instead. Now all PC's see each other and it is simplicity itself to set up.
Sorry just read thread title, both Windows 7 here's a video which shows you how to set up a homegroup. Network.