New computer build graphics issue.?

I build a computer the other day, a budget gaming rig. The parts are: AMD Phenom II x4 955, 4gb Kingston HyperX Blu, Seagate 250gb 7200rpm (just a spare drive I had), DiabloTek DA 600w, ASRock 870 Extreme3, Windows 7 Ultimate x64, and nVidia 8400gs PCI. The issue is with the graphics card. I have absolutely no intention of using this for long, a Radeon 6870 is in the mail, but as it's not working well now I'd like it fixed. What it's doing is pretending the video card has no drivers. I installed the drivers from nVidias site (195.62) and the nVidia Control Panel is apparently operational, I can switch screens and change settings, and even OC the card with RivaTuner. Aero even works, but there are these tiny things that point to it not working. In DXDiag, it says that it is running DirectX 11, when the card is DX10, and when you press Ctrl+Alt+Del, the screen draws from the top down rather slowly, and the in-game performance (or lack thereof :D ) is rather sloppy even for the 8400's usual s**tiness. What is it doing wrong? BTW my monitors are 1440x900 and 1920x1080.