clearing my purchase history as well as all the history on my menu

Is there a way to just completely wipe everything out and start fresh? I would think that there would be away to do that because if you collected this reciever and gave it to a new customer all my purchases and history wouldn't show up. The problem is my ex-boyfriend had purchased some very nasty movies and now its on my history and my purchase history when I hit my menu button, my fiance is about to move in and I don't want him to see these. Any suggestions?

Thanks