Can I use my TV as a second monitor?

The problem is simple: broadcast quality television just isn't the same as a computer's video display.

At best a regular TV display is around 640x480 resolution. Years ago, when personal computers were first introduced to the mass market, they were actually designed to use TVs as monitors, at a default resolution of 320x240, if I recall correctly. (Anyone who had an Apple ][, as I did, will remember the 40 character display width.)

Today, many video cards don't even go down to 640x480 any more. 800x600 is a common starting point, and even then - you've probably got it set higher, since most computer monitors support resolutions of at least 1024x768, if not much, much higher.

Resolutions that simply won't work on a normal TV.

Those "TV's" on your favorite computer shows? They're not regular TV's at all. They're actually computer monitors that support the resolution required to properly display the computer's output.

So. What are your options?

If you can take your computer down to 640x480, you can try connecting it to your TV. Many laptops actually include an "s-video" out for exactly this purpose. Depending on your laptop, it may be treated as a mirror of your laptop display, or as a second monitor, or you may be able to switch between them. You will quickly see that the quality of the display is, likely, very, very poor.

If S-video is not an option, there are converter boxes available from places like Radio Shack that will take a standard VGA connector and turn it into a composite video signal that can be plugged into a TV with a composite input. In general, this results in roughly the same poor quality computer display.

Surprisingly, in both of those cases, video playback can actually look quite good. What I mean is that if you're using your TV as a computer monitor and to do typical things like reading email or surfing the web, you'll be quite disappointed. However if you are playing back a video - say playing a DVD in your computer and watching it on the monitor - it seems to be quite acceptable. My theory is that most DVDs and other videos are targeted at exactly the TV's resolution, and that, plus the fact that for video we're "used to" that resolution, our expectations for that type of display are simply met.

Oh, and as to using it as a second monitor - to mirror what's going on on your primary computer screen: many laptops support using both the internal LCD screen and the VGA (or S-Video) output at the same time, so you may be able to simply hook it up. If you don't have that option, you'll need to get a splitter of some sort that will allow you to take your computer's monitor output and send it to two different devices: your regular computer screen, and a VGA converter box as I described above. Alternately you could purchase a video card that supports TV-out, or supports dual screens.

Now, there is salvation on the horizon, but it'll require a new TV. Newer TV's are going digital, and many do, in fact, have digital (DVI) input - particularly those that are High Definition (HD) ready. In these cases you actually stand a chance of being able to connect your computer directly to the TV. The TV may not support the same higher resolutions that your computer monitor might, but they'll almost certainly support resolutions that are much more acceptable for computer usage.

(All this is based on my own set of experiences some time ago attempting to do exactly what the questioner was asking. If there are particularly new or novel solutions to this problem that I've overlooked, I'd love to hear about them too. Just leave a comment below.)