This method is rarely possible to put into practice. However, it may be useful to you to increase security for your computer data. Maybe you are doing the work and then out to rest and eat. So, no need to shutdown your computer or take off. Therefore suitable for use in this way.
Right Mouse Click on desktop> New> Shortcut
Message will come out of the box 'Create Shortcut'. Please type the code below into the box> Type the location.
rundll32 User32.dll, Lock Workstation
In the box labeled 'Type a name for this shortcut' type LOCK MY COMPUTER or whatever you want.
Now that you have set an icon on your computer desktop. You just double click the icon and see what happens.
For additional security, you can create a user account with the password in the control panel.
best of luck. :)