I want better graphics for my pc for gaming what kind of video card can i get?

I have a Toshiba with an AMD Phenom(tm) II N640 Dual-Core Processor 2.9Ghz, 3.7GB of ram, with an ATI Mobility Radeon HD 4200 Series video card which i wish to upgrade please help me out in any way.|||Those are laptop specs and unless your laptop supports a discrete graphics card (and this is rather doubtful) you cannot upgrade the onboard graphics chip- sorry mate but that duck ain't gonna quack!|||you can't upgrade laptop video cards.