MacBook won't recognise External HD

OWC makes excellent external drive enclosures. I have had many over the years, all have worked perfectly with all of my Macs.

It's a good idea to have an external drive for backups.

The most likely 'problem' is the generic caddy and its USB interface, although it may be the drive itself. Even though it may work on one Windows pc, that does not mean it meets the (ahem ... stricter) requirements of macOS. Also, the Seagate 7200.10, while it was a good drive in its time, it is very old, discontinued around 2009; and it had a known firmware bug and caused a lot of complaints among Mac users. Also, the fact that your Win7 PC also doesn't recognize the drive is an indicator the problem is with the drive and/or enclosure, not your Mac or PC.

It *does* have a partition, even if only one, that could be either Master Boot Record or GUID - which one would have to be verified. Macs can read NTFS formatted drives but if your drive isn't working (for whatever reason), it may not be recognized.

jefffrommillom wrote:

I also wondered if I could use Boot Camp assistant to partition my Mac and install XP on that to then be able to read the external HDD.

I doubt that would be a solution and you probably cannot install XP on it anyway.

I agree with @MartinR that the generic caddy is most likely the problem. Macs are very picky about the adapters, docks, caddies & enclosures. I've personally encountered these issues over the years. Your best options in my opinion are devices from Plugable, StarTech, and OWC as they are my go to brands for most supplies.

What, exactly, is the make & model of the HDD? What is its partition type & format?

And what exactly are you using to connect the drive to the Mac? Please provide make & model, or even a link to the adapter, dock, enclosure being used. Does the adapter, dock, enclosure have its own power supply?

Is it a 2.5" or 3.5" drive?

What happened to the old Windows XP PC? There is a chance the hard drive has failed.