Which Graphic Card should I buy?

[Ice_Black]

I would look at an HD5670 GDDR5.

What model number is your CPU and what model number is your motherboard??

CPU: AMD Phenom II X4 945
Motherboard: ASUSTeK Computer INC. M3A78-T Rev 1.xx (Bios Version: 2001)
Ram: 4GB (Two GB each)
DVD RW: Optiarc DVD RW AD-7241S ATA Device [Optical drive]
HD: SAMSUNG HD103SJ
HD: SAMSUNG HD502HJ
Graphic Card: ATI Radeon HD 4650 512MB
PSU: CORSAIR HX 520W MODULAR PSU

Windows 7 Professional (x64) Service Pack 1 (build 7601)

My PC, Monitor, Router and also HP ProLiant MicroServer is connected to "ASDA Surge Protection Extension Lead"... I wonder if that causing my PC to crash? But my MicroServer never had problem.

[a mastermind]

+1 to hd 5670. definitely better bang for the buck than named gtx.