utorrent .avi problem

I've been using utorrent for a while.
Just recently when I try to watch a .avi movie all i get is sound - no video.
Any suggestions on what i've done wrong. more importantly, how do i sort it?

 

Download and install the below, should fix you up.

K-Lite Codec Pack Full 3.20

 

Excellent. Worked a treat.
Should I uninstall AC3filter now???

 

If you installed it trying to get the AVI to play I would but it's up to you. Do you use it for any other audio decoder and processor filter?

 

The guy that built my computer installed it.
I never really knew what it's purpose was.
Would it do any harm to uninstal it and if there is a problem I could roll back the computer?
Sorry if this is really basic stuff but I'm still learning. I'm not a complete novice but there are still some basic things I should know, but don't fully comprehend yet.
Thanks for your time.