Office 2001 for Mac doesn't require activation - the Mac products have never needed activation, only Windows XP and Office XP (2002) and later require activating. For older Windows versions and all the Mac versions you just need a serial number that is valid - it doesn't matter how many times it's been used before, as there is no communication between your computer and MS telling them that you're installing it. With the newer versions that have to be activated you have to phone Microsoft after it's been activated several times and explain why it needs activating again, but as long as you've got a reason eg you just bought it second-hand, or reinstalled your PC or whatever, they will give you an activation response code.

It seems reasonably rare - I just checked on eBay.co.uk and two copies have been offered in the last 3 months, one selling for £28 and the other going unsold with a £26 starting price. Rather expensive then...
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