Can you tell me how to fix this problem?

I’m trying to watch a film but i get this error cannot find vids:div4 decompressor?

That’s one of the fourcc’s used by the divx 3 codec. (it’s the fast motion one - low motion has fourcc div3)
Get the divx 3 codec from here
http://www.divx-digest.com/software/divxcodec.html