.
Not "erased," "disabled."
Also, if microsoft decides the key has been compromised, then your cousin could have his installations locked down (disabled).
As you were advised earlier: 1) get a crack, 2) get your own key. There are no other safe options, and option 1) isn't particularly "safe," either.
And, if you need to ask "where I can haz teh crackz?" then you're better off going with option 2) because (I swear) I'll sell you to /b/ and let the channites feast upon your pain.