Use FREE & FREEWARE software
Monitor Off Utility
Turn off monitor is a freeware (also portable) utility to turn off monitor via keyboard shortcut. This software also can start screen-saver via keyboard shortcut. Both are can start by using mouse click. It works with Windows 7, Vista and XP but need the .NET Framework 2.0 or later.
Download Link: http://www.dekisoft.com/download.htm