I recently tried to update my 2009 iMac (10.7.5) to maverick, I don't have mountain lion on it so I'm pretty much skipping that entire update. Anyway when it downloaded and said it needed to restart. I restarted it, so far no problems with the update a little restart will be quick and easy. My iMac rebooted and showed the apple logo and a little 'thinking circle' started below it. And it did that overnight and most of a day, still nothing, the same old screen.
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