You can't put a laptop graphics card in a dekstop. What graphics card you get will be dependent on your resolution and also the rest of the specs of a system. If you get a cheap computer at walmart you will also need to buy a power supply raising the price even higher. So a $400 computer turns into a $600 computer.
This is why I said you can save money, find a used core 2duo desktop with a decent card. Half the price for the same performance. Post the link to whatever you find. If you don't want to save money and buy used, there are better places to get a computer at a lower price and more performance, new. What is your budget? Do you need a monitor? I doubt you will want to build it yourself, although it is as easy as plugging in stuff.