Apple Macintosh PowerBook 150 - Manual (Page 124)

m You may have added a control panel or extension that is incompatible with
other programs you use. Restart the computer, holding the Shift key down,
until you see the message “Extensions off.” If this solves the problem,
remove any control panels or extensions you recently installed.
You just did something you didn’t mean to do.
m If you have not yet taken any other action, you can usually undo your most
recent action (even if you aren’t sure what it was). Most programs have an
Undo command in the Edit menu. Choose Undo to go back one step in
your work. In most programs, you cannot undo more than one action.
See the documentation that came with your programs for more information
about their operation and features.
116 Chapter 9