@tomos: Thanks for the heads-up re BDJ for Aomei Backupper. I shall d/load it.

Once the Free AOMEI Backupper Pro v4.1 was downloaded, I couldn't figure out - HOW THE HECK DO YOU REGISTER using the key sent separately via email?
Others had asked this Q in the discussion thread at BDJ, but there seemed to be no answer as yet.

At the time of installation of this latest version, my installation does not ask for a key or anything. It just works.
The installer removed an earlier Pro version that I had and asked if I would like to keep the key, or something, so I said "Yes".
I wonder - is that how it "registered" - i.e., automatically using the old key?

...It sounds like yours is registered, but hard to know...

Yes, I was fairly sure that was likely to be the case.

Interestingly, in the BDJ discussion thread @Pequi Smith said:

The license is tied to the Machine ID. So if you upgrade from 4.0.6 to 4.1.0 and elect to keep the registration(it will ask), it will upgrade to a registered version of 4.1.0. Which is what happened to you (and me).
If you clone the partition to another HD, the registration will be invalid since it uses the HD serial number (and other stuff) for the registration algorithm.

Copied from: AOMEI Backupper Pro - Backup and Restore Software - 100% off PC - <http://www.bitsdujour.com/software/aomei-backupper-professional#comments138248>;

I was aware that the registration was probably attached to the Machine ID but not that it was attached to the HDD ID also. That could be a good reason for NOT using AOMEI Backupper Pro.
For example, in this Mini-Review, I originally used AOMEI Backupper FREE to clone a failing HDD on my laptop to a new HDD. I then replaced the failing HDD with the new (cloned) HDD, and the laptop worked perfectly - including AOMEI Backupper FREE, which I used to test it all out after the switchover.

However, if the registration was attached to the HDD ID also, then I would presumably not have been able to have done this using only AOMEI Backupper Pro throughout, because the registration would have been rejected due to the new/changed/unrecognised HDD ID.

If this is the case, then it could probably serve as a good example of the sorts of knots that software vendors can unintentionally tie themselves and the user up in when they try to create a rock-solid and loophole-free registration key/process. This sort of thing could tend to be frustrating and detract from the perceived utility/value of the software to the customer - and there is evidence of that frustration in the discussion thread. There is also significant frustration shown regarding the apparent inconsistency of virus reports from downloading the installer software from the same and/or different sources. These points/problems do not seem to have been adequately addressed by the vendors in the discussion thread, so I would suspect that the BDJ result for this software giveaway might be somewhat less than its potential might have been, and that frustration could have created negative consumer confidence in AOMEI products.

Despite this, I think that my live trial of the software in this Mini-Review demonstrates that AOMEI Backupper FREE is a brilliant tool. That would probably go for AOMEI Backupper Pro as well.