How To Enable/Disable Fast User Switching In Windows 7, Vista, XP

A single computer is often shared between multiple users, Windows XP, Windows Vista, Windows 7 makes it easier for users to share a computer using the Fast User Switching feature enabled, it allows more than one user to log on simultaneously at a single computer, for example, if you are currently logged onto a computer, another user can log on to watch movies, without you having to close your open programs and log off. Once the user is finished, you can return to your session where all your programs will still be running.

In Windows 7 / Vista – Method 1: Using Local Group Policy Editor

Click Start, type gpedit.msc in the Start Search or Run dialog box and press Enter.
Now navigate to the following location:
Local Computer Policy > Computer Configuration > Administrative Templates > System > Logon

To Disable Fast User Switching:

Set Hide entry points for Fast User Switching to Enabled. By enabling the policy, Administrators can hide the Switch user button in the Logon UI, the Start menu and the Task Manager.

To Enable Fast User Switching:

Set Hide entry points for Fast User Switching to Not configured for enabling Fast User Switching.
not configured
Group Policy Editor does not exist in certain editions of Windows Vista. Alternately, you can change the settings via the registry.

In Windows Vista – Method 2: Using Registry

To change settings via registry, follow these simple steps:
Click Start, type regedit.exe in the Start Search or Run dialog box and press Enter.
Navigate to the following branch:
HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Policies \ System
Create a DWORD (32-bit) Value named HideFastUserSwitching by right clicking on the right side of the editor and selecting New >  DWORD(32bit) Value.
Set the Value data for HideFastUserSwitching to 1
value data

In Windows XP

Open Control Panel and then User Accounts.
user accounts
Click Change the way users log on or off option.
Check Use the Fast User Switching check box and now click the Apply Options button.
And on the contrary, if you want Fast User Switching to be disabled, leave the checkmark unchecked in Fast User Switching option and click the Apply options button.