!MapInfo 6.5
The version of MapInfo we have is not the latest version, but nobody seems to mind and I've never seen any students use it or heard any teachers ask to make sure it was installed. Therefore I would assume it is not used much. 
!Installation
Install MapInfo from CD or ISO, don't worry about the DBMS support, that stuff comes with Windows versions > 98. 
If you lose the key, you can find it by opening up another copy of the software and checking "help"->"about"
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There was a semi-fiasco in 2007 where database which was thought to be a Mapinfo database was left unreadable and a lot of work had to be redone.  We never actually figured out what happened.