heres what i would do with your money: go town to the nearest budget computer parts store or computer fair
pick up the following parts
put computer togther, and enjoy
AMD athlon 64 3500+ venice - $299
DFI LandParty nF4 Ultra D - $198
1GB Corsair TwinX 3200C2 - $189
Antec Smart Power 2.0 500W - $112
Elsa ATI Radeon X800XL 256 MB - $352
Logitech x-530 5.1 speakers - $92
Sony 16x DVD Dual layer burner - $48
Samsung 16x DVD ROM - $30
Western Digital 200GB 7200rpm HDD - $116
Samsung 930BF 19" 4ms LCD - $729 [ no need to skimp on monitor]
Antec Super Lanboy Case - $120 [ a good case if u wanted to mod]
Logitech Deluxe Keyboard - $20
mouse either:
Logitech Mx525 optical gaming mouse - around 60$ of 1600 dpi goodness
or the god of mouses, Logitech G5 laser mouse - 85$
chuck it all togther, leave some wiggle room, in pricing for a few exstra heatsinks, some thermal glue etc [using the g5 mouse in this price]and we come in at
$2 450
not bad considering the parts used... this would be one sweet gaming computer, if any1 wants to tweak this build to get it closer to the $4000 budget feel free, iam sure u could sink some money into a better keyboard or an insane cpu like the new AMD Athlon FX-57, $1505 of raw cpu speed
so there ya go, i made u a comp for 2500 bucks, and u have 1500$ left to go spend on some kick ass games