Free Microsoft Software
There are a number of free software programs out there, some more useful than others.
Here's a list of Microsoft Programs that I have found that are totally free and in most cases, fully functional.
Microsoft Office 2010 Starter (Includes ad-supported versions of MS Word and MS Excel)
Microsoft Security Essentials (XP, Vista, W7, W7-64bit)
Microsoft Word Viewer 2012 (lets you view a Word file, but not edit it)
A free alternative to MS Office is Open Office which works with MS Office files.