Vista to Windows 7 Upgrade Problems.. Please help?

I have a dell xps m1530 with windows vista home premium. I recently upgraded to windows 7 by doing a clean install. Now whenever i want to play a game, it says that directx is not detected even thought the computer says directx 11 is installed. Also for some games it says video card not found even though the system comes with an NVIDIA GeForce Go 8600M GT with 256MB GDDR3 card. Please help me rectify this problem.|||download 'games for windows live'|||I suggest you go to the Microsoft site and get answers from their experts.