Lock Computer - Create Shortcut

0. By default, you can also press the Windows + L keys to lock the computer.

1. Right click anywhere on your desktop, and click/tap on New and Shortcut.
2. Type rundll32.exe user32.dll,LockWorkStation and click/tap on Next. 
3. Type Lock Computer for the name, and click/tap on Finish.
NOTE: You can name this shortcut what you like though.
4. You are done. Now next time you want to lock your computer, simply click this shortcut. That’s all. Enjoy!
 http://www.sevenforums.com/tutorials/13278-lock-computer-create-shortcut.html