poproks :
I would prefer AMD and ATi, but if it has to be, Intel and Nvidia is just fine. Thanks again! -poproks
I'm afraid 400 dollars isn't going to give you anything capable of being a decent gaming computer nowadays if you NEED a computer now, I would go for an intel i3-2100 build using an H67 mobo, and utilize the onboard graphics until you can buy a separate graphics card.
My best suggestion though, would be to wait for a while and save ~$150 - $200 more dollars for the computer. Plus, AMD's bulldozers are right around the corner, so after you save that money, some new things might come out that are better suited for the budget gamer.
I'm running on an i3-2100 and a Radeon 6850, which you can get on a budget build for around 550-600 dollars.
EDIT: an example of the first suggestion
http://www.newegg.com/Product/ComboBundleDetails.aspx?ItemList=Combo.634248