This is as simple as heading to the Microsoft web site, locating the page for MS Office 2007, and clicking the Download button. On a DSL connection, this download should only take a few minutes.
The program Microsoft Office 2007 is not free to download for Microsoft customers. You will have to pay the upgrade fee after the provided trial period.
They're essentially the same program - BUT - the 2010 version will contain enhancements such as bug fixes, files to work with new hardware & software etc.