Windows Media Player 11 not showing AVI video

Windows Media Player 11 is playing the audio of .avi video clips, but
not the video. Instead, it shows a visualization.

Until today, I had Windows Media Player 10, but hardly ever used it. I
decided to try it, and selected "Update" on the "Help" menu. After lots
of struggling, it updated to WMP 11.

I'm very unfamiliar with the program, and would prefer to stick with
Irfanview, but now Irfanview isn't working either. It plays the audio
with a blank screen when trying to play these files.

I'm afraid to try WMP 11 with other file types, in case it's the program
itself which is messing them up.

My operating system is Windows XP Media Center Edition (I didn't want
it, but I'm stuck with it), but the year shown when I updated WMP was
"2005", though I think it should be 2004.

It's an almost-new Gateway laptop.