Apple iMac (21.5-inch and 27-inch, Mid 2010) - Manual (Page 45)

45 Chapter 4 Problem, Meet Solution
Problems That Prevent You from Using Your iMac
If your iMac won’t respond or the pointer won’t move
 Make sure your Apple Wireless Keyboard or Apple Magic Mouse are turned on and
the batteries are charged. (See “Replacing the Batteries” on page 47.)
If you’re using a USB keyboard or mouse, make sure they’re connected. Unplug and
then plug in the connectors and make sure they are secure.
 Try to force problem applications to quit. Hold down the Option and Command (x)
keys and press the Esc key. If a dialog appears, select the application and click Force
Quit. Then save your work in any open applications and restart your iMac to be sure
the problem is entirely cleared up.
 If you’re unable to force the application to quit, hold down the power (®) button on
the back of your iMac for five seconds to shut down the computer. Unplug the power
cord from your iMac. Then plug the power cord back in and press the power (®)
button on your iMac to turn it on.
If the problem reoccurs when you use a particular application, check with the
application’s manufacturer to see if the application is compatible with your iMac.
For support and contact information about the software that came with your iMac, go
to www.apple.com/guide or to the manufacturer’s website.
If the problem occurs frequently, try reinstalling your system software (see “Reinstalling
the Software That Came with Your iMac” on page 54).