I have been looking into rebuilding my desktop because that is one of the procedures that you are supposed to do every now and then. so... this is what I do...
PROCEDURE:
Restart.
Press and hold COMMAND + OPTION at end of startup (before desktop appears).
Dialog box appears, asking if you want to rebuild the desktop.
Click on OK.
I do that and nothing happens. It boots up normally! How can I get into that thing???
Mac + Rebuilding Desktop 
Linear Mode
