I use two programs to test video - VirtualDub and TMPGEnc.
They're both free off the web, so are quite a few others. With
either you can load a video (except MS .asf format AFAIK and
other "lesser" formats like.rm .ram .mov or .viv which need 3rd
party players) and find out its encoding, fps, sample rate and
so on. You can then either re-save it in a different format or know
what codec to go look for (at somewhere like the codec warehouse)
to play it in its original format. They are both also good for editing
video - eg dropping frames or reducing display size to make
smaller files, repairing keyframes etc. I've never removed a
codec from my PC and must have quite a few installed by now,
and have no problems

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