watching mpeg video file from a data disc

i copied a video i made for a friend and put it on a data disc. when they tried to play it on their PC only the audio worked.
they tried media player/winamp etc, and it said something at the bottom of the program about 'codecs'.

does anyone know what is wrong/how to fix it/what to download to get this to work or is it just not possible?

thanks for any help you can give, bearing in mind that i dont know a huge amount when it comes to this type of thing!

I’d suggest feeding the file into a diagnostic utility like avicodec (http://avicodec.duby.info) to find out what codec is missing. If you need further help paste to us what avicodec says.