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My circa 2008 iMac hung up today and wouldn't reboot -- it just hung on boot with the Apple logo and the spinner. I booted the Snow Leopard DVD and ran Disk Utility on the drive. It told me the drive needed repairing but during the repair cycle stopped, and said the drive couldn't be repaired. That I should format it and restore from a backup.

So I did. Or, am doing. The restore from my TimeMachine drive is about 75% done now.

Even if this is successful, I'm nervous. I'm not sure if that drive failure was some sort of uncorrectable filesystem corruption that occured because when the iMac was hung up I hard stopped it with the power button, or if the drive is starting to fail.

I'd like to replace the drive in it just to be on the safe side. Is this hard to do? I couldn't find anything about this procedure on Apple's support web site. If I replace it is there a brand of drive that I should buy or is the OS accepting of anything I put in there? Is it a 2.5" or a 3.5" SATA drive in there?

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If you're talking about an aluminum iMac, getting to the HDD involves removing the built in display monitor to be able to get behind it. YouTube seems to have several video walk-throughs that show the process (including this one; the link is to the first part). Additionally, a quick search turned up a site with written, step by step instructions. The process seems too complex to provide here.

If you're comfortable with this level of complexity in hardware repair, then the video or text walk throughs should help you. I suspect, all things considered, if you're not confident enough to perform the upgrade yourself just by looking at videos of others who have done it, then this probably falls into the class of "take your iMac to your local Mac service centre and get them to do it": yes, it will cost you money, but they can also guarantee their workmanship...

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Wow. That's far more involved that I thought it'd be. Thanks for the links. I'm taking this one to the depot for repair. – Ian C. Feb 8 '11 at 19:59

Yes, this is hard to do. Go to and look up the repair guide for your particular version of the iMac to see just how difficult.

You can use any 3.5" SATA drive in the iMac. Choose a replacement drive based on your criteria such as capacity, price, manufacturer's reputation, etc.

The drive should report its S.M.A.R.T. status in the Disk Utility application. If this status is good, I wouldn't bother replacing the drive.

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the SMART status for the drive was reported as fine. Can you see this follow-on question? It's still not booting after a restore and Disk Utility still says there are unrecoverable errors on the drive. Thanks! – Ian C. Feb 8 '11 at 20:05

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