I have a Nvidia GeForce4 in this machine and it supposedly supports HD resolutions... with a DVI to component cable that is, to quote Nvidia, "rare and difficult to find".

This isn't a problem if your TV supports RGBHV (five-plug) input. You don't need a DVI-to-component cable, just a VGA-to-RGBHV cable, which you can even make yourself with a little care and sweat (I did). Heck, some TVs even come with VGA inputs.