Did anyone in here read the OPs post?? The OP stated his video card has an S-Video output. S-Video is 480i only, so if the video card that output, it will downrez whatever resolution the computer is set to to 480i. My old sony is currently hooked up and working on S-video with the resolution set to 1024x768.
to the OP: what model video card is it? many older ATI video cards (and possibly others as well, but ATI is what I have always used) have an S-Video connector, but they will output composite with the correct cable connected.