Vista - Help! Trouble with Movie Maker and .AVI files

I recently bought a new laptop for school, which came with Vista. Although this is my first time owning a computer run with Vista, I have had some experience with the system before.

When trying out windows movie maker, I noticed that each time I imported a .avi file, it would not play. Only the auido worked properly. I have had pleny of experience with WMM in the past, and never before has this probem occurred. I thought maybe something was wrong with the actual video files, but when I tried playing them in other programs, they worked just fine!

I started researching online, and found these forums. I read many different threads that described similar/the same problem that I am dealing with...but no one seemed to have a solution.
One suggestion I read was to install certain extra codecs...a link was give, so I went ahead and downloaded the codecs to try it out. But the codecs didn't seem to do a thing. My .avi files still won't work in WMM.

This is aggravating, because I work with Movie Maker quite frequently, and the files I use are most often .avi files.

If anyone could lend a hand, I would appreciate it so much! Maybe I am still missing the correct codecs? I'm not sure! I just know that I would like to find a solution as soon as I can.

Thank you for your time!