These seemed to have worked for me when media player didnt load on windows 7. (wmp 12 : Remember you cant uninstall/reinstall windows media player, but you can add/remove from windows components. I dont think doing this fixes any driver issues like a fresh install would).
Ran this as Admin on command prompt. If you are using UAC, then All Programs -> Accessories -> Right click on CommandPrompt and select run as admin
1.) sfc /scannow
2.) If sfc doesnt work, then on the same command prompt try
type "regsvr32 jscript.dll" and press enter.
type "regsvr32 vbscript.dll" and press enter.
Also worth having some registry cleaners check you registry. Tweaknow seems to work best for me.
HTH