Fast User Switching provides a possibility to switch quickly beetwen users without loggin off. Follow these instructuins in order to disable or enable fast user switching option:

 1. Go to "Start", "Run" type "services.msc" (without qoutes) and press enter.

2. Open "Fast User Switching" and then change "Startup Type" to "disabled" (this will disable loading service at next startup). 

3. Right click on "Fast User Switching" and click on "Stop" (it will stop service immediately).

In case if you need to enable Fast User Switching just change "Startup Type" to "Automatic" and reboot your computer.

It's strongly recommended to use UAC (User Account Control) active in your Windows Vista because UAC improves the security on Windows Vista. Under some conditions you might want to disable it, for example some users don't want to click on additional mouse click to allow some program/task to be executed.

Solution #1 - Using MSCONFIG

1. Launch MSCONFIG by from the Run menu.

2. Click on the Tools tab. Scroll down till you find "Disable UAC" . Click on that line.

3. Press the Launch button.

4. A CMD window will open. When the command is done, you can close the window.

5. Close MSCONFIG. You need to reboot the computer for changes to apply.

You can re-enable UAC by selecting the "Enable UAC" line and then clicking on the Launch button.

Solution #2 - Using Regedit

1. Open Registry Editor.

2. In Registry Editor, navigate to the following registry key:

• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System

3. Locate the following value (DWORD): EnableLUA and give it a value of 0.

4. Close Registry Editor. You need to reboot the computer for changes to apply.

In order to re-enable UAC just change the above value to 1.

Solution #3 - Using Group Policy

1. In the Group Policy Editor window, browse to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options.

2. In the right pane scroll to find the User Access Control policies (they're down at the bottom of the window). You need to configure the following policies:

3. Reboot your computers.

Solution#4 - Using Control Panel

1. Open Control Panel.

2. Under User Account and Family settings click on the "Add or remove user account".

3. Click on one of the user accounts, for example you can use the Guest account.

4. Under the user account click on the "Go to the main User Account page" link.

5. Under "Make changes to your user account" click on the "Change security settings" link.

6. In the "Turn on User Account Control (UAC) to make your computer more secure" click to unselect the "Use User Account Control (UAC) to help protect your computer". Click on the Ok button.

7. You will be prompted to reboot your computer.

In order to re-enable UAC just select the above checkbox and reboot.