Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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Can I Boot iMac From External Drive

Is it possible to boot iMac from external HD?

If so,I have a WD 1tb external drive that I can use.

My iMac is only booting to a white screen.I'm thinking my HD is dead.

I have a WD 1tb external drive that I can use.

The drive has a ton of stuff on it so I really don't want to go to the trouble of formatting and erasing the drive until I know for sure whether or not I might possibly use it for booting the ailing iMac.

Since I only have the white screen,I don't have the option to use disk utility on the iMac.

Already tried booting safe mode,install DVD,etc,etc.

I don't have another mac to try target mode.

Answered! View the answer I have this problem too

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You can use a USB, FireWire or Thunderbolt connected drive (HD or SSD).

The real issue is prepping the drive so it has the needed partition setup GUID and partition Mac OS Extended (Journaled). Then you need to have to install the correct OS-X your system can run with.

I would get a USB Thumb Drive (64GB) find a friend (or a working second system) that's a similar model and using Disk Utility on his system prep the Thumb Drive and install OS-X on it. Once you get there first try altering the boot disk using the control panel to see if your Thumb Drive boots your friend's system. If it does shut the system down and give your system a try. In your case you'll likely need to use one of the Startup key combinations for Intel-based Macs.

Once you get your system up see if you see the systems HD. If you do then use your other external HD and copy off anything thats important (backup). Then using Disk Utility try repairing the disk. - Good Luck!

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Thank you for the answer,Dan. I have one close friend with a Mac but they won't be back in town until next Friday. I'm surrounded by PC users but that doesn't help this particular problem. Maybe I'll figure something else out or I'll just have to wait for my friend to get back home.


Dan, I am currently in the process of doing exactly what you have suggested. However, it isn'y being too successful. I have used the disk utility on a new iMac (bought yesterday) and downloaded the OS X onto my WD external HD. I have then tried to start up my old Mac using the option key and using the external HD to boot it up. I am on my 3rd time trying today and it only seems to get a quarter way through then nothing more. How much time do I give it?

Is the new OS X too powerful?


Are you sure the external drive you are using as the boot drive is prepped up correctly? For now lets not try your system just working off of your friends iMac (new system) can you get the external drive to boot it up? USB2 is slow so be patient.


I would be working off of a USB thumb drive (32MB) for this don't mess with your WD 1 TB drive!


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Yes you can dear Dennis Wilson

in order to save your data, turn on your imac and quicky press T. your imac will be in target mode.

get a thunder cable and connect it to another imac or macbook, and a new external hard drive will be detected. open that and copy your files to external drive or just create a folder on the desktop and past all files in there.

open disk utilities and repair your drive, if not successfull erase it. insert your external hard drive and create an image of the imac that you're are using. use disk utilities or carbon copy to do it, and save the same image on the external hard drive. disconnect the hard drive and connect it in your imac, turn it on and press alt key.

choose your external hard drive as startup disk, use your friend user name and password to login as administrator. once logged in. open disk utilities or carbon copy and create an image from your external hard drive to your imac drive. once you are done shutdown your imac and start it without your external hard drive. (u mighty need to press alt to choose your imac drive to startup with). use your friends credencials to login again.

good like.

steven picasso

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@steven picasso - You may want to reread the OP's post "I don't have another mac to try target mode" so Target Mode is not an option for him.


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Dennis Wilson will be eternally grateful.
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