You need a nice enough video card that comes with a TV out feature. Mine does, its a Nvidia Geforce 4. Also, most if not all of the ATI All-in-wonder series video cards have this feature.

This allows you to switch easily between you computer monitor and computer.

Or, you could get a VGA to RCA converter. (Ebay it)

what kind of hookups do you have for your TV?

I tryed using my RCA out with my video card to run one of my old crappy cheap TV's, but, It does not look good due to the low resolution of many Tv's. For instance, regular computer monitors will have a resolution of 1024x768 pixels, while a TV would only have as little as 480x360 or less. So obviously unless you have a really nice TV with a good resolution your not going to get the quality image that your used to on your monitor on your TV.