I dunno,,it's on craigslist, i thought once it was downloaded and "certified" on a computer, they were "one and done"
I would be weary of it if it is on Craigslist for that amount
could be a pirated copy, could be Non-genuine, could have already been used / activated / validated.............. there for not being worth .0004 cents to your own needs.....
also, you did not tell us if it was an Upgrade to win7 Pro ( and if it is 32 or 64 bit either , not that it matters )
myself, some of my family members and even some close Squaddies got burned several years ago purchasing a bundle of 10 win XP Pro licenses...... turned out they were all pirated/non-genuine........... and the worst part of it in my view is that we purchased them from one of my Family Relatives that actually dealt with redistributing/selling software..... ( he is not a relative anymore, and was not a Close relative at the time....... )
I turned his arse in .. reported him
TC