Start Task Manager by right-clicking the Taskbar, click the Performance tab
     and note the value for Uptime near the lower-right of the screen.
 
     - or -
 
     Run the following from a command prompt:
          systeminfo | find "System Boot Time:"
 
     The output will look something like this:
           System Boot Time: 11/12/2013, 1:23:45 AM

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