P4 2.6C - BX80532PG2600D - $174.00
ABIT IS7 - IS7 - $99.99
Corsair XMS 512mb - TWINX512-3200LLPT - $135.00
Total for that is just over 400, drop 50 on a burner - (samsung, plextor, several others - depending on color and whether you want dvd playback at all). Then you'll be right at 460.
that's how i'd do it with that money.