This is a post by Aaron Shaw on PTC site.
Have you downloaded Creo 4.0 yet? One of the first things you will want to try is the new full-screen mode. It removes everything but geometry from your view, so you can work more directly with your model. Here are some tips for using the new capability:
Switching Full-Screen Mode On and Off
To switch to full-screen mode: Press F11 to enter full-screen mode or click the Full Screen icon in the status bar. The ribbon model tree and status bar disappear and the graphics area expands to fill the window.