unrecognized/mislabeled file

[agent222]

I have a file that supposedly when decompressed is an .mpg file. The trouble is after I decompress it, WMP, and, other such media players don't recognize it, &/or say that there are codecs missing from it. I thought of Gspot, but it doesn't recognize this file as well. Are there any other similar programs to Gspot that can tell if there are codecs missing, or, even what the true file extension is?

[Baldrick]

avicodec, videoinspector, http://www.videohelp.com/tools?s=38#38