Ok, my problem is on my imac7 I think its called its a desktop mac with everything in the screen, I have been trying to install os x Yosemite onto it , and all I get now is it "installing on maintosh hd" then it shuts down. then I have to hit the on button for it to power back up and repeat what it just did. I am trying to fix this for a friend so I am not that knowledgeable with macs as I am with pcs. I also tried restarting into safe mode by holding down shift with no luck at all. thanks