I’m going to build a computer for my friend. All I have is the hard drive with windows xp on it. He doesn’t really have any preferences except he wants to be able to play Call of Duty 4 and the Half- Life series (HL2, ep1, ep2) He just wants the games to be playable (doesn't have to be on high graphics). His budget is $500. Any ideas for each computer on the computer. He’s going to do everything with a 17” CRT monitor until he has more money to upgrade. Preferably I would like the stuff from newegg.