At work we had an upgrade so they threw a whole bunch of old PC's away. I took one for this use. The specs are as follows:

Pentium 4 1.8Ghz
384MB Ram
DVD

That's pretty much it. I've got a 400 and 250GB sata hard drive in my main pc which I would like to move to the server as this is where the bulk of my files will go. I'll stick my 150gb Raptor back in my PC. I've just bought a new sata pci card to run the hard drives off. I won't need a monitor as I'll administering it remotely. The server comes with an ATi 128 rage pro card though and I tried unsuccessfuly to start the server without the card so it will have to just stay there for now.