hello Mac Forum! I have a 2009 iMac is x version 10 running on Yosemite ~ ( I have not updated to the latest software because I read it gives you problems in iPhoto and I use my iPhoto a lot.) lately it has been giving me problems such as randomly shutting down. Today I tried turning it on and it starts to boot up but instantly shuts down. I unplugged it for a while and than tried again to no avail. I noticed that the screen seems dim, not its usual brightness. I tried starting the diagnostic but it won't have it. I am worried about my photography files. Any advise on what to do? Thank you!