Check out the page
http://www.nirsoft.net/utils/nircmd.html 
1. Download the ZIP file (link is at the end of that page).
2. Extract it to a temp folder.
3. Run nircmd.exe file.
4. Click "Copy to Windows directory", click Yes.
5. Now, right-click desktop (or inside any folder like Start Menu, Programs, Quick Lauch) and select New>Shortcut.
6. Enter "nircmd monitor off" or "nircmd monitor low" (no quotes please) (I don't know the difference between them. Experiment.).
7. Click Next, and enter "Turn Off Screen" or anything you like as shortcut name. (no quotes). Click Finish.
8. Right-click the shortcut you created, and click "Properties". Click "Change Icon"
9. If a message "The file %windir%\nircmd.exe contains no icons." (or similar) appears, click OK.
10. Choose a nice icon (In WinXP, I use the "blue power icon" of shell32.dll file).
11. Click OK. Click OK again.
12. Try out the new shortcut to get a feel of it!
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