How to Log Off of Windows Vista
If someone else is going to use your computer, you don't have to shut down your computer. You just need to log out of your user account so that another user can access his account. Follow these steps to log off the current user account of Windows Vista.
Save any open documents and close any open applications.
You want to make sure that you have all of your changes saved before you log off.
The Start button is located at the bottom-left corner of your screen.
Click the arrow next to the Lock button and choose Log Off.
Windows Vista logs off and displays a list of users.