First build list!

So this is the first build;
Case: This is based on a case/psu/keyboard/mouse/speaker combo pack priced at 45$
Power Supply: (included)
Ram: 2 Gigabytes DDR2 pc2 5400 667mhz ram 99$
Hard Drive: This is one I leave to you, Fry's Electronics has 250GB drives for 40$ if you watch closely but it is one category that is pretty hard to make a wrong choice with. Sadly they're up to 60$ each today.
Optical Drive: a basic Sony DVD drive 31$
Graphics Card: This one is up to you, But for my personal preference Nvidia+ DX10=Awesome (8800 GTS 320mb) 280$
Processor:AMD AM2 socket X2 5000+ (combo with a motherboard)
Motherboard:ECS Geforce6100sm-m (At Fry's Electronics for 150 for this and the proccesor) Micro ATX, will fit in smaller cases too.

At 605$ this is an excellent deal. you get DX10 and an excellent dual core proccesor. Ontop of that all this needs is a monitor and operating system easily recycled from your old computer.