DRM removal problems: missing codecs when playing with Windows Media Player

I have purchased 2 drm removal programs which are Soundtaxi, and Audials one/Tunebite. Both say that they have to convert the music videos I bought on iTunes if they will play on windows media player, Real Player, or Quick time player. When I try to play them on windows media player and the others it says that I'm missing codecs. I have no idea what to look for on the internet(that won't give me a virus or something).
Does anyone know anything that would be helpful???
Please help.