Can't see or hear anything, but system says all codecs are installed

I'm new to Divx... completely clueless. A few pages back I found what I thought was my answer, an "essential" program that analyzes and tells you what codecs you need to run a file.

Well, I downloaded it, and it said that I had all the codecs installed, that Windows Media Player should be more than enough to handle it. But nothing happens, and when I try it with a dedicated Divx player it says the video contains "FOURCC Code '0'", whatever that is.

Help!