Media PLayer 11 Not Working

Okay, something wonky happened to my computer a few days ago and I did a
System Restore point (that thing is a life saver) but I accidentally erased
the computer created ones when I created my own. It was a dumb moment because
I know how it works.

Anyway, prior to that I had downloaded the new WMP 11, Windows Live, etc.
WMP 11 worked fine until the system restore point, in which when I had to
download it again, it started being funky. It opens, but only in mini player
mode. When I try to play and .avi video it doesn't work, and therefore my
videos that I have on Ares doesn't work either. Am I missing a codec or an
encoder? Help. I need my videos. LOL.