Daysleeper,
It would help knowing how much you want to spend, but for games, I would recommend:
AthlonXP 2500+ or higher
nForce2 Motherboard (With SoundStorm)
512Mb (2x256Mb) PC-3200
GeForceFX 5900XT or Radeon 9800Pro
80Gb 7,200rpm w/8Mb Cache Hard Drive
Dual Layer DVD Burner
If you want something with a little more kick:
Athlon64 (90mn Socket 939 the best option)
nForce3 Motherboard
512Mb (2x256Mb) PC-3200
GeForceFX 5900XT or Radeon 9800Pro
80Gb 7,200rpm w/8Mb Cache Hard Drive
Dual Layer DVD Burner
Take Care,
Richard