On this site click on advanced search - set the search to Software.
Try typing in Code Pack or Codec Pack Lite and you will be offered a few of these packs.
Don't install all codecs as this will seriously fuck with your computer as I fiound out 2 yrs ago I was getting red and green lines all down my visual display. Not Good!! :oops:
Anyway theres a codec in one of the packs called G-Codec or something along that lines, install it run it, and it tells you which codec was used to compress it.