Best possible gaming pc around $600

Do you also need an OS? Putting a gaming computer together with a monitor and OS for $600 is nearly impossible. Here's a build without an OS for just over $600:

Antec Three Hundred + BP430 Black Steel ATX Mid Tower Computer Case 430W Power Supply - Retail
http://www.newegg.com/Product/Prod [...] 6811129065 $79.95

AMD Athlon II X2 240 Regor 2.8GHz 2 x 1MB L2 Cache Socket AM3 65W Dual-Core Processor - Retail
http://www.newegg.com/Product/Prod [...] 6819103688

GIGABYTE GA-MA785GM-US2H AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813128394

http://www.newegg.com/Product/Comb [...] mbo.273663 $119.99 (CPU + motherboard combo)

G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK - Retail
http://www.newegg.com/Product/Prod [...] 6820231166 $79.99

SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
http://www.newegg.com/Product/Prod [...] 20f3%20500 $54.99

SAPPHIRE 100284L Radeon HD 5750 1GB 128-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814102859 $129.99

ASUS VH222H Black 21.5" 5ms HDMI Widescreen 16:9 Full HD 1080P LCD Monitor Built in Speakers 300 cd/m2 1000:1 (ASCR20000:1) w/ SPDIF out - Retail
http://www.newegg.com/Product/Prod [...] 6824236053 $159.99 - $10.00 MIR

Total - $624.90 - $10 MIR

Windows 7 will add $100 to the build unless you're a student. You can get it for $30 if you're a student.

Microsoft Windows 7 Home Premium 64-bit 1-Pack for System Builders - OEM $99.99

or

www.win741.com