Introducing the Ribbon
The 2007 Office release is designed to help you work more quickly and with greater ease. In the 2007 Office system programs Word 2007, Excel 2007, PowerPoint 2007, Access 2007, and parts of Outlook 2007, an important feature of the new design is the Ribbon, which runs across the top of the program window and replaces menus and toolbars. With the demise of menus and toolbars come new, easier ways to carry out tasks - including new keyboard shortcuts.
Why the change? A lot of research has been done into how people use Microsoft Office, and how they wish it would work. The new look is the result of all this research. Commands and features are now grouped together to reflect the way they are used. So you'll have to do less searching around as you work.
Note: In all "non-Ribbon" programs in the 2007 Office release, keyboard shortcuts work exactly the same as they always have.