My 2004 single 17' flat imac's screen gave a good little flicker and then displayed a message that I must turn my computer off from the back and restart it. When I do this half the time it finds the OS but half the time it looks for a while before displaying the same message. When it finds the OS it works for 5 to 10 minutes then displays the same message. What are my options? I think it may be a cooling fan due to a lack of the deep hum that is normal for it. Help!
It could also be a corrupted hard drive, or your Mac OS X installation has been corrupted. Try to retrieve any data you have, then do a fresh install of the OS.