About the 'lowest' recent version you can get is Office 2010. At the moment, Office 2013 is having some teething troubles, so I'd be inclined to stay away from that.

IMHO, unless you believe you need access to the features that have been added to Word 2007 & later, you're probably just as well off staying with Office 2000 until you need to upgrade to Win 8 or later. That said, I do note that Office 2000 isn't actually compatible with Win 7, so it might be advisable to upgrade to at least Office 2003 (you should be able to pick up a legit copy on ebay fairly cheaply). Office 2007 & later have an entirely different 'menu' structure that will take some getting used to - a lot of people complained when they first encountered it and 6 years on I still see people posting in various forums asking how they can get the old menus back.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]