I'm running a Windows 7 desktop computer and I've got a Nvidia GeForce 6150SE nForce 430 graphics card. My games lag way too much (Sims 3 lags so much it's difficult to play, and Slender lags so much I can't play at all!). I've been checking into different video cards but I really know next to nothing about what makes a good video card or which one would make my gaming experience better. Any suggestions?