If your computer is located in a place whereaccess it from unwanted people, and turn on and off each time it does not allow you to work rhythm, then you should learn how to lock the computer when leaving the workplace.
Fortunately, it is not difficult.
Each time getting up from the table, just clickthe keyboard shortcut WIN (this key with a painted on its windows a symbol by pressing the "Start" menu launches) and «L». The computer is locked and access will be possible only after entering the password.
If you want the computer to blockedautomatically open the display properties tab "screen saver" and tick the item "Password protection". Now, after some time of inactivity, the system will include a screen saver, again to continue the work it will be possible again only after entering the password.