The aspect ratio of an image is the ratio of the width of the image to its height. For example if we have an image of 1024 by 768 points, that means that we have a ratio of 4:3 (4 points horizontal, 3 vertical)
If you want to get some more information on ratio, two interesting links are:
http://www.cinemasource.com/articles/aspect_ratios.pdf (local copy attached)
Most of the projectors that we have installed in campus, are a 4:3 ratios, so for most of them, having the external monitor configured to 1024 x 768, will work best.
In Windows 7, you can change your screen resolution following these instructions:
There are some exceptions to the screen ratio of 4:3 on campus, that are wide screen, they are:
Education Century XXI lab, that has a 16:9 ratio. Recommended resolutions: 1280 by 720, or even 1440 by 810 will work too. Another one that should work too is 1024 by 576, but it is not very common
Education Room 111, has a ratio of 16:10. Recommended resolutions: 1280 by 800, or 1440 by 900. You can also do 1024 x 640, but it won't look very nice
Please contact us if you need help setting up these resolutions. Sometimes they are not listed in the normal windows change resolution page!