I've always thought that I may not be able to prove that I have two hard-drives and the FSDreamteam may penalize me in conviction of sharing my software with another user.
First, if you have 2 hard disk, you'll just use 2 activations of the 6 you have available, but your hardware ID will not keep changing when you *switch* your hard disks multiple times, you should have only 2 different hardware IDs, and only if the hard disk you are switching is also your Windows boot disk (so, you have 2 different Windows installations as well).
So, even by reinstalling multiple times, you should only consume 2 of your 6 activations, because your are working with 2 hardware IDs at the most (unless you change other things as well), and not the hardware ID should not change if the hard disk you are switching is a secondary one, not the one you are booting Windows from.
However, even assuming one day or the other you WILL finish your 6 activation, first there's the built-in provisioning that, if more than 90 days have passed since the last time you got a new activation, the oldest ones will be reclaimed automatically, so the server will grant you a new activation.
If this is not the case, and you will need to request a manual reactivation, when we check the activation log, we don't simply get the hardware ID fingerprint of your system, but your IP number as well, which is useful exactly in cases like this, so you don't need to "prove" you are yourself, because different hardware IDs will still have the same IP number, or at least the same network and, even if from different networks (es. you use 2 different ISP or you changed it), at least in the same city...
Note that, we usually never refuse an activation. In the 2 years we have been running FSDT, it happened only 1 or 2 times, and it was a clear case of abuse, like multiple activations requested in a very short amount of time (like few hours between them), with multiple IP numbers, belonging to entirely different networks and in different countries too so, it was quite obvious the product was used by different people because the serial has been shared.
If the situation is not so obvious, we'll always grant a new activation.