Possible Duplicate:
When reinstalling Windows 7, does the language, version, architecture (64-bit or 32-bit) or source (OEM, retail, or MSDN) matter?
Theoretically, can you activate Windows XP, Vista, 7, on identical machines? For example, if peter and tom got the same machines at BestBuy, can they activate Windows 7 on both machines since the hardware ID / fingerprint is the same?
I think the normal use is to activate it multiple times on the same machine on different partition, for example, if Win 7 on one partition is slowed down by various app installation, then reinstalling Win 7 on a different partition as a fresh start is allowable.