As explained many times on the forum, an activation request might be triggered when EITHER changing hardware OR changing the boot drive, and, it's possible it happened because you did BOTH at the same time while updating the BIOS too.
However, is not certain this might have been seen as a new hardware, because the system is able to make a difference between a whole new system, or just a new hardware ID from the previous system.
As also explained many times too, the whole hardware detection strategy is done *entirely* outside our control, by the Esellerate engine. We don't know exactly what parameters are looked for, and we can't even change the policy.
But, since we DO know if you did an hardware upgrade or you installed under an entirely new system (because the difference IS logged on the server), in the unlikely case you'll ever run out of activations, and have to ask for additional ones, since we see the difference, it's fairly obvious we won't have any problems granting you additional activations, when it was clear that, for example, out of 6 reactivations, you made 5 upgrades to your existing hardware.
Not that we usually raise any problems anyway, we denied additional activations in very obvious (and very rare) abuse cases, such as users activating 3-4 different PCs from different part of the world in a very short time (like few hours apart), we had some users that had over 30 additional activations added, because all their requests were logged as hardware *upgrades*, not new systems.
And of course, if you SUSPECT you MIGHT lose an activation because of your maintenance, if you DEACTIVATE all your products BEFORE upgrading/restoring/reflashing your system, you'll gain an additional activation, so your counter won't go up after you reinstall everything.
And again, don't forget there's *another* safety measure in place, which is the 90 days from your last activation, which mean, even if you forgot to deactivate, you have used all your activations, and you can't contact us for any reason, IF your last activation was obtained more than 90 days earlier, a new activation will be granted anyway automatically, even if you have used all your available ones.
I really don't think there's ANY software activation system out there that has some many safe measures to prevent the case of not being able to use the software, and has such user-friendly policy.
