My GTX 460 has an hdmi out. My LCD monitor has an hdmi input. Usually I use DVI... can I use an hd cable for gaming? Would it improve image quality, or is this only a feature for connecting a pc to a large TV?
Yes you can use the HDMI cable to connect to your monitor. In some cases (depending on GPU capability) this may also allow you to transmit audio through the HDMI to the monitor (though I'd bet the speakers in the monitor suck).
To be honest, I don't see why not to use the DVI cable when connecting to your monitor.
Basically speaking, the HDMI cable is simply a DVI-D cable with a different pin arrangement and carries audio. As long as good quality components are used for both there should be no difference in image quality.
Ok, but what about if I want to hook my pc up to a 42in tv? I did this with both DVI and S-video, neither of which produced a good quality image. My resolution was limited to 1027x728 (or something along those lines), whereas my monitor has a native 1650 x 1050. would the HD change that equation?
It is a Sony 42in lcd, and it wasn't even 1280x720, it was the next step down. I was trying to play empire total war, and it worked, but the resolution was so low that it was pretty crappy image. Same goes for a 48in DLP... couldn't get above 1024 x 768. Weird.
S-video only goes up to 720x480 and it is interlaced so if you're using that it's going to look crappy, DVI should look much better, 1024x768 isn't that low and is likely native for your LCD (many older ones are), but it would be unusual for a DLP tv to be that resolution.