Windows 7: Ctrl+Alt+Del and Start Menu - Add or Remove Switch User

This will show you how to add or remove the Switch User option in the Windows 7 CTRL+ALT+DELETEscreen, Lock Computer screen, and Start Menu arrow menu for all users on the computer.

Through the Local Group Policy Editor

1. Open the Local Group Policy Editor.

2. In the left pane, click on to expand Computer Configuration, Administrative Templates, System, and Logon.

3. In the right pane, right click on Hide entry points for Fast User Switching and click on Edit. 

4. To Add Switch User to CTRL+ALT+DEL Screen

A) Select (dot) either Not Configured or Disabled.

B) Go to step 6.

5. To Remove Switch User from CTRL+ALT+DEL Screen

A) Select (dot) Enabled. 

6. Click on OK.  

7. Close the Local Group Policy Editor window.

8. Restart the computer to fully apply.

ref: http://www.sevenforums.com/tutorials/63025-ctrl-alt-del-start-menu-add-remove-switch-user.html