depends how cheap you are looking to go?
You can do it easily for $400, or you can spend $800.
$400 would be AMD motherboard with 6150 geforce video built in ($70), Athlon II x2 240 ($50), 4gb DDR2 memory (2x2gb - $85), Blu-Ray drive ($60to$80), spinpoint 500gb harddrive ($50), and any case&400watt power supply combo you can find in the $60-$70 range