Apple Mac mini (Mid 2011) - Manual (Page 52)

52 Chapter 4 Problem, Meet Solution
Repairing, Restoring, or Reinstalling Mac OS X Software
If you have a problem with your Mac software or hardware, Mac OS X provides repair
and restore utilities that may eliminate problems and can even restore your software
to its original factory settings. You can access these utilities from the Mac OS X Utilities
application, even if your computer isn’t starting up correctly.
Use the Mac OS X Utilities application to:
 Restore your software and data from a Time Machine backup.
 Reinstall Mac OS X Lion and Apple applications.
 Repair your computer’s disk using Disk Utility.