S939 X2 4200+ and several Pentium 4's ranging from 2.4GHz to 3.2GHz. They're not mine per se, but they're either close friends or family's computers that I do all the maintenance on. I can't convince anyone to upgrade from their Pentium 4's. 🙁
Oh! I built something for my girlfriend's son to play games on a while back. I purposely used old components because he was three at the time and the chances of it getting trashed were fairly high - AMD something-or-other at 1.2GHz, God knows what motherboard, 512MB of memory, Radeon 9800 XT, and a glowy case. It still plays all of his games to this day, and he's turning six in April. 😛 Except for spilling juice near (not on) the keyboard once, he's been absolutely excellent at taking care of it (so good in fact that they bought him a netbook this past Christmas), and he now types better than he writes...