All items listed are available on Newegg.com.
The machine build listed here is more than apt enough to handle the latest games with ease.
Not listed are an OS, Monitor/Mouse/Keyboard/Speakers. It is assumed someone already has a copy of a popular OS they can place on here (legally!) using their old key, and that they already own mundane peripherals.
This beast is good looking, unique, cheap(!), and can slaughter most games out today.
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Mobo and Processor - $259.99 (Combo)
AMD Phenom II X4 955 Black Edition 3.2GHz Socket AM3 125W Quad-Core Processor
Item #: N82E16819103674
ASUS M4A78-E ATX AMD Motherboard
Item #: N82E16813131368
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Cheap, Sturdy, Stylish Case - $49.99
Sunbeam ACIII-T Transparent Computer Case With Side Panel Window
Item #:N82E16811166006
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Reliable, fast, big HDD - $59.99
Western Digital Caviar Blue 640GB 3.5" SATA 3.0Gb/s Internal Hard Drive
Item #:N82E16822136218
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FAST Ram (Good timings), from a reliable vendor. Come with Heatsinks. - $50.99
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500)
Dual Channel Kit Desktop Memory
Item #:N82E16820231166
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Front access to Audio/USB/Cards. - $21.99
nMEDIAPC ZE-C98 All-in-one USB 2.0 Card Reader with USB/IEEE 1394/e-SATA Port/HD Audio Ports
Item #:N82E16820132020
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POWERFUL, cheap, stylish PSU - $72.49
OCZ StealthXStream OCZ700SXS 700W Power Supply
Item #:N82E16817341019
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2xPowerful, low cost, MODERN video cards in Crossfire configuration - $199.98
SAPPHIRE Radeon HD 4850 100245L Video Card
Item #:N82E16814102770
Grand Total: 751.41 Before shipping.