you can go through as many hard drive as you want
i.e. if your hard drive fails you can install a new one on the same mobo and it will still be legit
if you switch mobos it will no longer be valid if you use the same product key
now on a side note
once you get the new machine up and running
get another hard drive the same size as your primary
then dl and install
this program
it will clone one hard drive to another
it just needs to be equal or larger in size
someone might be saying whats the point?
if your like me
and you are on a very tight budget
you will want to save that $400+ worth of software
includeing your Windows product key
if you make regular clones
like when you purchase and install software
if your hard drive fails
then you will still be able to boot into a working version of your PC
personalized, customized, and just the way you left it
just my $0.02