Let me just cover one extra base.
When you use a computer to connect to an analog TV device, the signal must be converted to analog, and then needs to be interlaced to work on a television. Any card with TV out (whether it be S-video or an RCA) can do this fine, but the picture will NOT look as clear on the TV as it does on the monitor. Therefore, use of a television as a display device is only recommended when you are presenting images that are large and clarity is not important.
Let's take a scenario - you want to present stuff on a TV for an audience. The television you are using is a 27inch non-progressive (or HD) television. The things you want to present are your actions on a Windows-based computer - actions like opening windows, clicking on icons, typing text, etc. Large things, like opening a window, would show up fine. Clicking on an icon would work, but it may become difficult to make out the picture of the icon or the text underneath. Typing text will be problematic, unless you make effort to either zoom in or enlarge the image to make it more viewable. This is due to the lack of detail that the TV will support.
There are some workarounds to improve this method. Windows 98SE, Windows ME, and Windows XP will support more than one display at a time. This allows you to alter the resolution of each display device separately. For a television, to make small detailed things appear larger, I would change the resolution of the television to 640X480. This may cause some minor problems for you and it may not.
If you are trying to use the television as a large monitor AND as the primary display on a computer, I recommend against it. As I said, you will lose clarity and even if you are up close, the detail lost will make it even harder for people to work on the machine. I don't think this is what you were trying to do, but I thought I'd point it out anyway.