reset xbox to orginal state

I got an xbox from my friend that was already softmodded. Somehow i think this guy did it wrong because i can notrestore ms dash nor delete the unleash x dash from the hard drive and get rid of it completely. So i have no backup of original dash. I heard someone say that you make a disc with files on it and it automatically puts the original dash back in order and gets ridof evo xand unleash x. Any help?