TRICK 1: First create a new shortcut on your
desktop using a right mouse click
and enter 'rundll32.exe
user32.dll,LockWorkStation' in the location field.
Name the shortcut what ever u want to like abc.
Then just double click on it and your computer will
be instantly locked
TRICK 2: The Windows key + L also does the same
thing
AND THEN TO UNLOCK CLICK ON UR ACCOUNT NAME....