Here is an awesome Codec Pack, designed especially for Windows 7, and is known as Window 7 Codecs. You just need to download the exe file, and run it, done!! All the codecs have been installed, no need to play around with anything else.
Installing Windows 7 Codecs will allow you to que up the following formats in your Windows Media Player – amr, mpc, ofr, divx, mka, ape, flac, evo, flv, m4b, mkv, ogg, ogv, ogm, rmvb, xvid.
Under the start menu you can also find the ‘Settings Application’, using which you can configure and play around with other settings, as shown below.
There are lots of customization options in this, however to keep you safe ‘Reset All’ button is there.
So, go ahead and grab this Codecs Pack, and play everything (almost) in your Windows Media Player.