Apache is not running from XAMPP Control Panel ( Error: Apache shutdown unexpectedly. This may be due to a blocked port)

I have installed XAMPP (xampp-win32-1.8.2-0-VC9-installer.exe) on Windows 7 successfully. But unfortunately, the following error was found during running Apache from XAMPP Control Panel:

5:38:38 PM  [Apache]    Error: Apache shutdown unexpectedly.
5:38:38 PM  [Apache]    This may be due to a blocked port, missing dependencies, 
5:38:38 PM  [Apache]    improper privileges, a crash, or a shutdown by another method.
5:38:38 PM  [Apache]    Press the Logs button to view error logs and check
5:38:38 PM  [Apache]    the Windows Event Viewer for more clues
5:38:38 PM  [Apache]    If you need more help, copy and post this
5:38:38 PM  [Apache]    entire log window on the forums