Hi Everyone, Appreciate you looking at this thread to help! I have just received my iMac (2010 i3, 21.5" ) back from a computer shop. They said they had it running all night and all was well but when I turn it on it will restart after about 5 mins ish. They had Yosemite running on it. I thought maybe there was an issue as I was trying to update the OS via the Mac AppStore so in the end I tried to reinstall the OS via Time machine. Nope, it keeps restarting and then gets stuck on 16% and doesn't move. Left it all night and nothing still the same. Tried Internet Recover. nope just keeps restarting. I'm not sure what to do now as it just boots into diagnosis mode. Any thoughts?