Office 2007 Overview: The Button
The Microsoft Office Button located at the left side of the Ribbon replaces the old File menu. It provides access to commands for all the things you can do with a document: open, save, print, publish, etc.
The right side of the Button menu contains a list of recently-opened
files. To keep (pin) a file in the Recent
Documents list,
simply click 
[pin].
When a file is pinned, the button looks like a push pin 
viewed
from the top.
The Button menu also is where you can go to change application preferences. Click [<application> Options] at the bottom of the Button menu, and select a category to update from the list that appears.