Have you ever just wanted a box dedicated to email or a PHP/Apache sandbox that isn't already being used as a real server or workstation? Don't go out and buy a new Dell or other new machine just to fill the test server, firewall or other non-resource-intensive need. Instead, get a corporate castoff from Retrobox. They've got no-OS machines that yesterday were sitting on some Fortune 500 developer's desktop. They've got decent machines for server and firewall purposes for $50, usable workstations for under $100, etc. At the very least, check them out before looking elsewhere.