How do I do screen mirroring with a macbook?

Question

I have a late 2009 macbook with lion 10.7.5 and cannot get this to work with my projector.
I tried to mirror the display, but the computer tells me this feature is disabled.  The computer worked with the projector in the past before updating...
I am using a USB connection.

Answer 1

Taking Screenshots in Mac OS X
Command-Shift-3: Take a screenshot of the screen, and save it as a file on the desktop
Command-Shift-4, then select an area: Take a screenshot of an area and save it as a file on the desktop
Command-Shift-4, then space, then click a window: Take a screenshot of a window and save it as a file on the desktop
Command-Control-Shift-3: Take a screenshot of the screen, and save it to the clipboard
Command-Control-Shift-4, then select an area: Take a screenshot of an area and save it to the clipboard
Command-Control-Shift-4, then space, then click a window: Take a screenshot of a window and save it to the clipboard
In Leopard and later, the following keys can be held down while selecting an area (via Command-Shift-4 or Command-Control-Shift-4):
Space, to lock the size of the selected region and instead move it when the mouse moves
Shift, to resize only one edge of the selected region
Option, to resize the selected region with its center as the anchor point
Source: http://guides.macrumors.com/Taking_Screenshots_in_Mac_OS_X