Ok first let me start of by saying back your stuff be for re installing I learnt my leason hard last time when I lost all my stuff after failed currupted hd :(     soooo this time round I have just saved over 270 gb of my data to external drives and all so sent it again to my time machine back hd. So it can't escape this time :p.        I'm restoring My computer becuase it now rejects any button I press on my wireless.mouse     so I won't be back on for a while  ={   sorry if miss spelt things I'm typing this from my phone