Personally I have stopped using Microsoft Office because there are Office-like software out there for free that work just fine for me. Right now I'm using OpenOffice 3.3 and use mainly Calc (its equivalent of Microsoft Excel). For email instead of Outlook I use Mozilla Thunderbird with the Lightning plugin for calendar/appointments.
I did try out Libre Office 3.4.1 which is a spin-off of OpenOffice. Apparently the original developers didn't like the direction Oracle was going with OpenOffice and decided to create a new office suite based upon Open Office . Unfortunately LibreOffice, specifically its spreadsheet program, kept crashing on me so I had to uninstall it. Maybe I will try it again in the future.
Anyways if you are insisting staying with Microsoft Office you can probably get the 2007 Version on eBay for like $50 depending on if you need Outlook.