What connection are you using between the computer and TV?
What is the exact make/model of your TV?
What is your output resolution between the PC and the TV?
Typically on this type of connection you will use a HDMI or a DVI cable between the PC and the TV, and if not, you would use a VGA cable. Using a composite video cable (yellow RCA cable) is absolutely NOT what you should be doing.
You want to match the output resolution of your PC to the exact resolution of the display you are connecting to. So, if the TV is 1280x720, you must set your PC to be putting out that resolution on the connection you have made.
It is also possible that the TV simply wasn't designed to play nicely with computers. Since it's a TV, it may only work well with 1280x720 and 1920x1080i HD resolutions, which may always produce a somewhat blurry image from a PC. Often, some TVs would only work with specific computer resolutions such as 1024x768, which didn't match up at all with the native resolution of the TV itself, and would always look blurry.
Newer TVs typically play very well with computers, but older ones definitely had issues.
