Troubleshooting computer monitor problems: the sideways stretch

The difference that you're seeing is that the "aspect ratio" of your new monitor is likely different than it was on your old CRT. This is a change we're seeing in the world of television as well as screens change from standard to high definition.

It's likely that your old CRT has an aspect ratio of 4:3 ... meaning that the width is 4/3 the height, or conversely, the height is 3/4 the width. Your new monitor is probably different. Perhaps it's 16:9, the new HD TV standard, but it could also be something else entirely.

If you look at screen resolutions, you'll see something interesting; measured in pixels, the old "standard" screen resolutions - 640x480, 800x600, 1024x768 - are all 4:3. And I'm sure that they displayed just fine on your old CRT.

I looked up your new monitor, and it has a native resolution of 1680x1050 pixels. That's not a 4:3 ratio (it's actually about 4.8:3, or more correctly 8:5). That means that's it's wider, in comparison, than your old monitor's 4:3.

Now, if you change nothing else and just plug in your new monitor, then the monitor needs to make a decision - how to display what is likely a 4:3 image in a 4.8:3 space. There are three choices.

The first choice is to maintain the aspect ratio of the original image:

This is typically done by displaying the 4:3 image centered within the larger screen. You'll see this all the time now when 4:3 standard definition TV shows are displayed on 16:9 HDTV screens. Typically, the centered image has black bars on either side to take up the unused space.

An alternative we almost never see is to crop:

In this case, the image is enlarged to fill the entire width of the screen while maintaining the original aspect ratio. The result is that the top and the bottom are lost since they don't fit.

The third option, and what I expect you are experiencing, is to ignore the aspect ratio completely:

In this case, the monitor stretches the image to fully fit the screen, ignoring the original aspect ratio. As you can see, what was a perfect circle at 4:3 is now a somewhat elongated ellipse when it's stretched to fit this wider aspect ratio. Everything on screen appears slightly stretched horizontally.

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That's all well and good, for way of explanation, but how do we fix it?

There may be two ways.

Your monitor may, in fact, have an option to choose what to do when the aspect ratio of what you're attempting to display doesn't match. In fact, your monitor includes the option to "Fill to Screen" (stretch, in the example above), or "Fill to Aspect Ratio" (the centered with black bars approach) in its settings. These are settings you would access using the menu and other controls on the monitor itself.

Many monitors include similar settings, but many do not. Your alternative is to adjust the screen resolution in Windows itself.

In Windows XP, right click on your desktop, click on Properties, and then click on the Settings tab. In Windows Vista, right click on your desktop, click on Personalize, and then click on Display Settings. In the resulting dialog, look at the Screen Resolution setting:

If you can, set the Screen resolution to the maximum native resolution your LCD monitor supports by adjusting the slider. In your case that's 1680x1050. If you can set it to that, then Windows will automatically display at the proper aspect ratio, and the monitor will not have to stretch anything. Setting your screen resolution to match your monitor's native resolution is, by far, the preferred solution to get you the best looking display.

If that specific resolution is not available, then you'll need to try resolutions that are smaller than that, but ideally with the same aspect ratio. 1512x945, for example, would maintain the same aspect ratio. Not all monitors handle running at less than their optimal resolution well, and it may result in a slightly fuzzy display, but it won't be horizontally stretched.

Finally, your friend may be right. If your video card cannot put out the monitor's native resolution, and you're unhappy with the alternatives above, then changing one or the other might well be called for.