My $40 Rig: "1GHz of Fury"
Okay, every single part in this computer was second hand, most from garage sales and friends, and a couple from Ebay. I would get a craputer, strip it, and put the best parts into what is now '1GHz of Fury'. I paid a total of $40 for the whole shebang, including case, drives, RAM, mobo, video card, capture card(s), sound card, thumping 2.1 speakers (massive sub on that one, cost $5 for that), mouse, keyboard, etc.
Processor: 1.2GHz Pentium III
Mobo: Asus P3B-F (I believe it's based on a 440BX)
RAM: 3x 256 1x 127 (or whatever, I really forget..)
Drives: 80GB WD, 40GB seagate, DVD combo drive (white, need to get a black one), 3.5" floppy drive (black)
OS: Windows XP Professional SP3
Case: Black aluminum with plastic front bezel. Tooless design. Three external bays and four internal HDD bays in a removable caddy.
Video card: I have an AVerTV capture card, a Radeon 7200 All-in-wonder, and an NVidia GeForce FX series as main. Two monitors currently hooked up, am going to ditch the GeForce and Radeon for a new card soon. ATi, probably.
I love this thing to pieces, and it runs lots of games really fast. I just tried Test Drive Unlimited, and got 7FPS. Get 25-35FPS in NFS:MW, and 14-20 in NFS: Carbon. Get 40+FPS in Urban Terror 4.1, and 30+FPS in MSFS9.