also not enough info on your PSU... may or may not be sufficient for your rig..
and as others said, add a stick of the same 512mb ram..(or if cheaper, get a dual-channel kit=better)
and if you want to do some decent gaming... get this card:
$79 after mail in rebate
there was also another decent card but it looks like newegg removed it.. the sapphire x800gto for $79 w/o mail in rebate..
edit: you also get a free copy of age of empires 3 w/ the card i recommended.. WHILE SUPPLIES LAST!!!!!!!!!!