In Word 2007, press Ctrl+Alt+[plus sign on the numpad] to turn the cursor into a 4-leaf clover. This will allow you to get into customizing keyboard shortcuts used inside of Word 2007.
At this point, if you want to know what a current keyboard shortcut does, you can press that shortcut while the clover cursor is up. Pressing Ctrl+P:
You can alternately click on any of the buttons on the Ribbon and assign them a new keyboard shortcut of your choosing just by clicking on that particular button including the function buttons at the bottom of menus (as indicated by the arrows in the following picture).
To enter a new keyboard shortcut, just click on the button and then with the cursor in the ‘new shortcut key’ textbox just press what keys you’d want to use. It will tell you if that shortcut is already assigned or [unassigned]. Just click the ‘Assign’ button and then the ‘Close’ button and test your new keyboard shortcut out.