Doubtful. But you still run the risk of having your key blacklisted. Besides...
Me, personally, only 2. One has Windows 7 on it (64 bit; in repair due to crappy display) and the other has Vista Enterprise (32 bit).
I have a valid Windows 7 Pro (x64) key and a valid Windows 7 Pro (x86) key.
But I was going to put it on some of my family members' PCs if they wanted it.