Decent gaming computer under 500

PCPartPicker part list: http://pcpartpicker.com/p/2YocB
Price breakdown by merchant: http://pcpartpicker.com/p/2YocB/by_merchant/
Benchmarks: http://pcpartpicker.com/p/2YocB/benchmarks/

CPU: AMD Phenom II X4 945 3.0GHz Quad-Core Processor ($80.98 @ SuperBiiz)
Motherboard: ASRock 970 PRO3 R2.0 ATX AM3+ Motherboard ($64.99 @ Newegg)
Memory: A-Data XPG V1.0 4GB (1 x 4GB) DDR3-1600 Memory ($30.99 @ Newegg)
Memory: A-Data XPG V1.0 4GB (1 x 4GB) DDR3-1600 Memory ($30.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: XFX Radeon HD 7770 GHz Edition 1GB Video Card ($105.38 @ Newegg)
Case: Thermaltake Commander MS-I ID ATX Mid Tower Case ($32.99 @ Microcenter)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Optical Drive: LG GH24NSB0 DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($99.97 @ OutletPC)
Total: $547.25
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-23 00:19 EST-0500)

As close as i can get, you need a discrete card to do anything half ass with games.
 
If you're going AM3+ it'd be a good idea to save up for an FX-6300

Otherwise

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Athlon X4 750K 3.4GHz Quad-Core Processor ($79.98 @ OutletPC)
Motherboard: Asus A55BM-E Micro ATX FM2+ Motherboard ($47.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($64.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: Sapphire Radeon HD 7770 GHz Edition 1GB Video Card ($74.99 @ Newegg)
Case: Thermaltake VL80001W2Z ATX Mid Tower Case ($21.99 @ Microcenter)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($16.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($99.97 @ OutletPC)
Total: $492.86
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-23 00:36 EST-0500)

That promotion on the XFX PSU will be over soon, you could get the Corsair CX430 instead
 

Vic 40

Titan
Ambassador
Looked at Roland's build and took a little bit faster cpu,a imo better case and it is a little bit over your budget=~$3,

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Athlon X4 760K 3.8GHz Quad-Core Processor ($84.74 @ Amazon)
Motherboard: Gigabyte GA-F2A75M-HD2 Micro ATX FM2+ Motherboard ($54.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($64.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: Sapphire Radeon HD 7770 GHz Edition 1GB Video Card ($74.99 @ Newegg)
Case: Antec GX500 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($16.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 (OEM) (64-bit) ($89.99 @ NCIX US)
Total: $502.64
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-23 05:54 EST-0500)

Changed some other things too like motherboard and windows,which is still the 64bit oem version of 8.1.
 
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-6300 3.5GHz 6-Core Processor ($117.12 @ OutletPC)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($94.79 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($64.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Case: Thermaltake VL80001W2Z ATX Mid Tower Case ($21.99 @ Microcenter)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($16.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($99.97 @ OutletPC)
Total: $501.81
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-23 17:51 EST-0500)

Discounts on the PSU and Memory will expire soon, here is an alternative (this PSU is not recommended for overclocking or stressful situations, so it'll still be best to get that XFX unit)

http://pcpartpicker.com/part/corsair-power-supply-cx500
 
Solution