LG 22X DVD Burner - Bulk Black SATA Model GH22LS50 LightScribe Support - OEM
Item #: N82E16827136168. $27.99
GIGABYTE GZ-X5BPD-500 Black SECC Steel / ABS ATX Mid Tower Computer Case - Retail
Item #: N82E16811233039 $39.99
Western Digital Caviar Blue WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM
Item #: N82E16822136218 $59.99
ASRock A780GMH/128M AM2+/AM3 AMD 780G HDMI Micro ATX AMD Motherboard - Retail
Item #: N82E16813157154 $69.99
Recertified: XFX PV-T96G-YHF GeForce 9600 GT 512MB 256-bit DDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card
Item #: N82E16814150425 $59.99
If OS is not needed
ZOTAC ZT-98GES3P-FSP GeForce 9800 GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail
Item #: N82E16814500059 $84.99
OCZ ModXStream Pro OCZ500MXSP 500W ATX12V V2.2 / EPS12V SLI Certified CrossFire Ready 80 PLUS Certified Modular Active PFC ... - Retail
Item #: N82E16817341016 $58.99
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK - Retail
Item #: N82E16820231166 $50.99
AMD Athlon II X2 245 Regor 2.9GHz Socket AM3 65W Dual-Core Processor Model ADX245OCGQBOX - Retail
Item #: N82E16819103687 $64.99
If OS is not needed
AMD Phenom II X3 720BE 2.8GHz Socket AM3 95W Triple Core Processor Model HDZ720WFGIBOX - Retail
Item#:N82E16819103649 $119.00
Microsoft Windows Vista Home Premium SP1 32-bit for System Builders w/ Tech Guarantee - OEM
Item #: N82E16832116674 $109.99
Subtotal: $537.91 (Before shipping, taxes (if applicable), rebates.)
Subtotal: $506.93 (Before shipping, taxes (if applicable), rebates.) If OS is not needed.
This is as close as I can get to 500.00 for a complete top to bottom system. Tight squeeze. If you do not need an operating system, that changes things a lot.
But you said from Scratch.
You still need to add a monitor, keyboard, mouse, speakers.