Automaticaly Lock-Out you computer if idle for 'X' minutes

Most of the cellphones now-a-days have this kind of feature by default activated.I felt it very secured , so searched the same for my laptop and as expected windows have included this feature inbuilt.

Goto Screensaver menu and watch-out there is a option of

"on resume,display logon screen"

Select the screensaver you want, then check the box to display the login screen when you exit the screen saver.  Enter the number of minutes you want to wait before your screensaver starts, then click Ok to save your settings.

Now, after the length of time you selected, you’ll see your screensaver as normal.
Then, when you move the mouse or press a key, you’ll see the normal login screen instead of your desktop.  Enter your password and login as normal to access your computer.

If you’re not fond of screensavers, you can lock your computer when you’re away without turning on the screensaver.  Just select None from the screensaver list, then check the box as before.  Now your computer will automatically switch to the Login screen whenever your computer is left for the amount of time you selected.