Multiple cards causing problems

Okay, my issue is this: I've had a GeForce 8800GT in my system for a while now running dual monitors. Everything was great, then I heard with Windows 7 that you can use multiple cards by different vendors, not in a SLi or Crossfire setup, just multiple cards. So I installed an ATI All in Wonder HD so I could watch TV and all that. I had plenty of hiccups until I'm here, where things seem to be working decently, but not quite right. Now that both cards are running, my tuner won't work. I tried Windows Media Center and ATI's Media Center, and neither will detect my tuner when the 8800GT is in. The other issue is that I'm trying to get my games to run on the 8800GT display, because obviously it's more powerful. Please help me if you can! Thank you.