By default the PowerBooks are designed to use the internal display as the main display. Furthermore, they are also set to run an external display as an extended desktop, rather than video mirroring. You'll have to set the PowerBook to use the external monitor as the main display, which requires access to the monitors control panel. Depending on how well you know the classic Mac OS, you can do it as I did once upon a time, by using keyboard shortcuts to select and open the hard drive, and then using some guesswork, figure out where the windows are and drag them over as you open them. Its difficult, but doable.