Microsoft Word

Not legally. But if you just want to read/edit and create Word documents you could try http://www.openoffice.org/ - a free Office-like app suite.

There is also StarOffice (from Sun Microsystems), available for free (not the latest version tho).

Or you could use WordPad which comes free with Windows to create basic doc files, & use the free Microsoft Word Viewer at http://office.microsoft.com/en-us/assistance/HA010449811033.aspx to open any Word file.