I tried playing an avi file in windows media player and the following happened. After starting it, the image went from normal to a vertical strip about 2 inches wide. This same file has been playing for several weeks.

I copied it to another machine where it played fine. Apparently something in windows media player has changed on this system. Is there a way to reset it to the default.

wmp ver 11.06
Vista
hp media center pc

Just to make sure, there is something wrong with your WMP, try to play same file on a same computer with different video player (Irfanview, Winamp, etc.)

I tried it with another viewer and it plays fine