Compaq sent out a rep to replace a bad computer chip on one machine I bought and at half the regular market price replaced all software missing from my open box specials. Ebay , auctions, and local computer shows are also excellent places to find bargains on computer hardware. The most obvious considerations for stock computer purchases are the amount of ram and raw horsepower to run applications like Windows 2000 server. The other factor is whether or not they came with a NIC or not and contained enough ram to run or help run a server. I have no specific hardware recommendations here other than to buy a networking kit.
Most kits contain a hub, two cables and two NICs.
Cables, hubs, and NIC are all relatively expensive when bought at retail individually. This is simply the most efficient way to buy the necessary equipment. Network professionals will often splice their own cable. I've always bought the best cables available from regular retail stores rather than computer stores who buy off-brand or make their own cable. I had the most trouble with unbranded cable and have often had to replace them very quickly.