HELP! dvi to hdmi makes worse quality!!!

It's a problem with Nvidia, they've been very terrible in supporting users with HDTVs. You can use the "resize my desktop" feature, but you'll have to find the registry hack to unlock it, because it doesn't show up on the 8800 series cards (From what I've read on the official Nvidia forums).

I have the same problem as you, but I'm using a 7900GS. I have to use a custom resolution which is a huge inconvenience, although if I use my laptop, which has an ATI GPU, it works fine. That is why I'm going over to ATI when my new video card gets here Wednesday. Other than that issue though, I really love my 7900GS and it's able to hit almost 6000 in 3dmark06 which is a real feat considering that I'm using it in Vista.