AMD Athlon XP 2200 43$ (Socket A)/AMD Athlon 64 X2 3800+ Dual Core Processor 132$ (Socket AM2) 

MSI MS-6330 Motherboard (25$) /MSI K9N SLI Platinum Motherboard (116$)[PCI Express] / MSI K9N Neo-F nForce 550 Socket AM2 ATX Motherboard (85$)

ATI Radeon 9550 256MB AGP Video Card (83$)/

512MB Ram DDR/DDR2 depending on motherboard (60$)

Western Digital 320GB UDMA/133 7200RPM 8MB IDE Hard Drive(111$) / Seagate 250GB UDMA/100 7200RPM 8MB IDE Hard Drive (88$)

Samsung 18x DL DVD±RW LightScribe IDE Drive w/SW  (35$)

Video Card (Choose according to motherboard) [max cost <100$ for 128MB]
ATi Radeon X700 256MB PCI Express Video Card w/TV-Out 70$ (PCI Express) <---- best buy
ATI Radeon 9550 256MB AGP Video Card  (90$)