How can I test and see which graphics cards are compatible with my computer?

I want this computer to run recent online games on high. Example: Warhammer Online, Age of Conan, and maybe even Crysis. Someone earlier said the graphics card wasnt good... I disagree it looked amazing.
Operating system
Genuine Windows Vista Home Premium with Service Pack 1 (64-bit)
Processor: Quad UPGRADE! AMD Phenom(TM) 9550 quad-core processor (2.2GHz)
Memory: 3GB DDR2-800MHz dual channel SDRAM from
Graphics card: 512MB NVIDIA GeForce 9500GS, DVI-I, VGA, HDMI
Hard drive: 320GB 7200 rpm SATA 3Gb/s hard drive
Primary CD/DVD drive: LightScribe 16X max. DVD+/-R/RW SuperMulti drive
Front Productivity Ports: 15-in-1 memory card reader, 2 USB, 1394, video, audio
TV & entertainment experience: ATSC-NTSC TV tuner with PVR, FM tuner, remote
Sound Card: Integrated 7.1 channel sound w/ front audio ports
Security software: Norton Internet Security(TM) 2008 - 15 month
Keyboard and Mouse HP keyboard and HP optical mouse

The Norton just comes with it, i'm getting AVG. Please help me out

The graphics on my computer will get distorted and then my computer will restart itself. I think it may need a new video card. The computer shop thinks it may be a virus and wants $39 to run a virus scan and then another $99 to remove the virus.. I use Advast for virus protection and don't find any when I scan it myself.

Will the shop be able to find a virus that I can't at home? Will a bad video card cause the computer to restart itself? Tell me your thoughts please.

I am using a 4 year old Gateway desktop pc currently with integrated video.