If you goto Google.com and type in Codecs you will get a number of codec sites that might be able to tell you which codecs are safe.

Or, if you are willing to install a different stand-alone player on your computer, you could goto http://www.divx.com and download and install their free divx player. That would install video codecs for you for their player and others, and as Divx is now an established and recognised product, I reckon it is very safe.

Mark