Genocidicbunny
Bug squasher
I ran that after I removed K-Lite and it said I had no Codec Packs installed.Try CCCP Insurgent if you're interested in fixing it.
If it was a single file, most likely a problem with just that one (or it didn't have sound.) I use VLC for trouble files like that, MPC for most others (because for some reason VLC doesn't have the same quality)
It worked fine on this pc before, and it worked on my laptop just fine as well, so it wasnt the file.