You my friend, have one KICK ASS PROCESSOR 4400, dual core. holllly crap.
and you have a nice case. You need a motherboard. I am not sure if this motherboard is entirely compatible or if any of the slots are right but all i know is u need an AMD antlon 64x2 compatible motherboard. I chose this one as an example but you can get a better one.
EDIT: Get 1gb or more of system memory (RAM) It will work great. Corsair is the best brand for that. Also, about your hard drive. I would suggesst change it. change it to a maxtor or a western digital. they seem to be the best brands