Build for $500

There is hope out there, you can get something for that. But the big questions is will you need a operating system?

This is an example of something you could do with 500. But that dosn't have a os in the build. If we have to include one we will have to drop back on a couple things which will cut performance.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Phenom II X4 965 Black 3.4GHz Quad-Core Processor ($94.99 @ Newegg)
CPU Cooler: Arctic Cooling ACALP64 Pro 36.7 CFM CPU Cooler ($14.99 @ Newegg)
Motherboard: ASRock 970DE3/U3S3 ATX AM3+ Motherboard ($69.99 @ Amazon)
Memory: Corsair 4GB (1 x 4GB) DDR3-1600 Memory ($19.00 @ Amazon)
Memory: Corsair 4GB (1 x 4GB) DDR3-1600 Memory ($19.00 @ Amazon)
Storage: Toshiba 500GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Newegg)
Video Card: MSI GeForce GTX 650 Ti 1GB Video Card ($123.98 @ Newegg)
Case: NZXT Gamma Classic (Black) ATX Mid Tower Case ($34.21 @ Amazon)
Power Supply: Antec Neo Eco 520W 80 PLUS Certified ATX12V / EPS12V Power Supply ($39.99 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($16.98 @ Outlet PC)
Total: $483.12
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-02-03 17:58 EST-0500)

for bang for your buck the 650 ti Out performs the 7770 as you can see in these benchmarks.

http://www.anandtech.com/bench/Product/680?vs=536