Samsung Compression Codecs

I can play most Movie Files from my Samsung Digimax 3500 Super, but ones that have been compressed cause Media Player 10 to give this error:
The file type is supported by the Player, but the file was compressed by
using a codec that is not supported by the Player.
Does anyone know a codec to download to solve this problem?
Is there a way to uncompress the file before Media Player 10 gets it?
Thanks
Glenda

To find out which codec you need use one (or more) of the tools listed on this page
http://www.moviecodec.com/questions/neededcodec.html