To enable Screen-Saver Password on Windows 7 pease open the "Screen Saver Settings" (Image-1)
# Method-1:
Press the key combination [Windows+Logo] [R] and enter this text, %systemroot%\system32\control.exe desk.cpl,screensaver,@screensaver
and press [ENTER]
# Method-2:
Start the "Screen Saver Settings" over "Start" >> "Control Panel"
>> >> "Personalization"
In the "Personalization" Window (Image-2) select (click) on "Screen Saver"
and now activate the option : "On resume, display logon screen"!
That iT's!
From here you can:
Conserve energy or maximize performance by adjusting display brightness and other power settings.
And/Or ... Chainge Power Settings in Windows 7
# Use your Windows password for your screen saver password
You can help make your computer more secure by creating a screen saver password,
which locks your computer when the screen saver is on. The screen saver password is the same password that you use to log on to Windows.
"Start"
"Control Panel"
"Personalization" 
