TigerDirect and NewEgg both have great prices on parts. Built my parents a computer for christmas last year. Triple core AMD processor & motherboard, 320gb HD, 600W PSU, 4GB RAM -- all that was only $350ish. Add in a DVD Drive and a case, you're only looking at around $400. Then if ya need a new Win7 disc, that's another $200. Still, for $600 you can build a computer that is worth about $750-$800 retail (and it will have quality parts in it).