to be honest your probably better off selling what you got
and grabbing a Athlon II x2 240 regor 2-4 gigs DDR3 and an AM3 board to be honest as that would give u a butt load more performance
as 2 gigs DDR3 = $55
athlon II 240 = $55
785g AM3 board = 60
sell the ddr400 and the x2 for a bit of change and your only out about $100 for a much faster system overall
just thats an old old setup
its lasted you good but if your gonna buy parts makes more sense to do a full swap