1. On a domain controller, Start > administrative tools > Group Policy Editor > Either edit an existing policy or create a new one (Remember its a computer policy you need to link it to something with computers in it, if you link it to a users OU nothing will happen).
2. Navigate to, Local Computer Policy > Computer Configuration > Policies > Administrative Templates > System > Logon.
3. In the right hand pane locate " Hide entry points for Fast User Switching" and select enable.