Problems with hard drive on 2006 Intel iMac

Since you have a screenshot showing Disk Utility reporting an "I/O Error" during partitioning I would assume the hard drive is bad.

As others have mentioned I would not spend any money at all on this particular model since it is known to have a lot of hardware issues.

The drive should be formatted to Mac OS Extended (Journaled) with a GUID partition. The disc that came with the computer, are you positive it is the original install disc? If it is not then you need to locate a Snow Leopard upgrade Disc (ebay still has them) but frankly you are dealing with a relic. I would not recommend spending a nickel on the computer as it is 100% worthless and really should be recycled, it is close to 15 years old now. If you want a Mac that would be more current then buy either a new one and if you don't want to do that buy a used one from a reputable reseller such as macsales.com or macofalltrades.com or even better an Apple refurbished Mac from Apple.

Also, please never ever post personal information such as serial numbers, e-mail addresses, phone numbers etc. in a public forum.

Does the computer serial number return "Early" or "Late" 2006"? If it is "Late," the disk may not be the originals—the Late shipped with 10.4.7 and Macs don't work with OS versions older than what was shipped.

Lookup: https://everymac.com/ultimate-mac-lookup/

To me, the 7.3TB reading and "Media Type: generic" sounds like something went terrible wrong when the original owner erased the drive.

I take it that the DU screen shot is from by booting from the 10.4.4 disks?

Are you comfortable with a diving adventure to extract/replace the old HDD?

Sorry if I breached forum etiquette by posting serial numbers, only did it to make it easier for people more knowledgable than me to help identify the problem.

No worry. Happens all the time. Not an etiquette thing as something Apple sees as a security issue. Not sure why.

but from what I have been able to Google on the subject, OS X 10.4.4 was indeed the system that these iMacs were shipped with.

Again, that would be the case if it is early 2006 but not if a Late 2006.

And rest assured I am fully aware that I am dealing with a relic :-) , but I happen to think it beautiful computer, and I am not looking for a more modern one :-)

Hey I love relics. Many of the senior contributors here fit that description, including me! I don't tell my age anymore but my Medicare card just had its 8th birthday. We have a number of old working Macs that are older than 2006. Cost is not an issue for me--I like to play with the old ones.

Are you up to replacing the HDD? Rereading the error messages strengthens my feeling that this HDD is "sleeping with the fishes."

Ursus1968 wrote:

Ok , so to update: I opened up the iMac and removed the hard drive. I then put it in a hard drive dock which I connected to my daughthers MacBook Air (running OS X Big Sur). The hard drive showed up without problem, and it showed the correct size (1 TB). Via DiskUtility I erased it and formatted it to MacOS Extended (Journaled). I put the hard drive back into the iMac and booted from the install disk. Starting DiskUtility, the hard drived showed up, but still showing the wrong size (7,3 TB)...

But I think it is strange that the hard drive appeared to work fine when connected to my daughters MB Air...

Hard drive technology drastically changed since OSX 10.4. This hard drive is a newer model WD hard drive which uses the Advanced Format technology which changed the default sector size from 512 bytes to 4K bytes. While some drives emulate the older 512 byte sector size it still may not be compatible with such an old OS. You will need to try and find a drive which uses the old style 512 byte sector size (or at least emulate it).

I would still be concerned whether that hard drive is health though since macOS did show an I/O error.

Edit: I should add that the SATA controller on this iMac may also not be able to handle the newer drive (or the perhaps the larger size).