How to enter serial number in About This Mac

If there was a logic board replacement, then the technician should have contacted Apple and registered the new logic board which would have had a serial number on it. There is no way for you to enter it anywhere as you would need to open up the Mac and then try to explain to Apple that the serial number needs to be registered in their system. I don't think that'll happen.

Not having a serial number, you will not be able to get any repair service (even if you want to pay for it) as Apple needs to have a serial number for any service process, so enjoy the Mac - hopefully you won't need any service.

Hello, t.r.ii.

It's been my experience that when the serial number goes missing from the About This Mac window, it's because the main logic board of the Mac has been changed for some reason, usually a repair, and the service tech has not encoded a new (or old) number into the ROM.

The lack of a serial number is not usually a problem when operating the computer, though it is possible for some random software to seek the serial number when registering an application after purchase. But this Mac and OS are so vintage that I doubt you'd encounter that.

If your OCD has come out to play and you feel you absolutely must program the number back into the system, you might google the process as there are (were?) third party utilities to facilitate that.

Otherwise, understand that the machine is well beyond any warranty service period that would require knowing the serial number, and you might as well forget it and just go about using the computer for whatever tasks you have in mind.

🙂

I'm happy to help.

I understand why you want to keep the iMac around. A 24" screen is nice when compared to the smaller Macs. I have one of the same iMac myself. In fact, I have several old Macs that I use to research issues folks post in these Communities. Yes, they do have longevity! 🙂

Did you get the issue with you Apple ID and password resolved?

You may have encountered a second problem: maybe the previous owner did not disassociate the Mac from their Apple ID account which would mean that you cannot set up an account with your own Apple ID needed for some Apple apps or services. At this point, it would be impossible to figure out what has been done with this Mac.