External Hard Drive not recognized on iMac Late 2009

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Level 1

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External Hard Drive not recognized on iMac Late 2009

i am trying to moves all files from 2009 iMac and just purchased a brand new Sandisk G drive. I was chatting with apple support and all the tips they recommended did not work. here are the steps they had me do.

Can somone please help, I just need the files and some pics. Since the Imac is so old, I am not able to log onto Icloud.com to upload. i have done all the steps to make sure the right boxes are clicked on finder but it still will not show up.

Earlier Mac models

Posted on Sep 9, 2025 10:53 AM

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Answer 1

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HWTech

Level 9

67,130 points

Sep 10, 2025 1:20 PM in response to jrcarmine56

You will want to erase the whole physical drive by using the instructions in the following Apple article:

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

If your Late-2009 iMac is running macOS 10.13 High Sierra, then you can use the APFS file system, otherwise you will need to use the MacOS Extended (Journaled) file system. If the Sandisk drive is a Hard Drive instead of an SSD, then go with the MacOS Extended (Journaled) file system since APFS can be slow on a Hard Drive and may even cause a Hard Drive to wear out faster. If it is an SSD, then either file system can be used, but the APFS file system has been optimized for use with an SSD.

If you want to share the Sandisk drive with Windows, then use the exFAT file sytem.

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Answer 2

rkaufmann87

Level 10

148,134 points

Sep 9, 2025 11:10 AM in response to jrcarmine56

What is the format type on the External Hard Disk, if you have not formatted it using Disk Utility (Applications - Utilities - Disk Utility) then the drive is almost 100% certain to be formatted for MS Windows which means the Mac cannot write to it.

Please watch the video in https://www.youtube.com/watch?v=7jIJwWqCTBI

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