Switch user in Windows Vista (without logging off)
Windows Vista allows you to have multiple users and user accounts on a single computer; this way, your data is protected, and each user can customize Windows the way they want, without affecting other users sharing the same machine. What you may not realize is that Vista can also have multiple users logged in at any given time: if another user needs your computer for a bit, you do not need to log off to let them back in: they can log in and out of Windows while you remained logged in. (The only exception being if they reboot the computer, in which case they will still get a warning message that other users are still logged in.) This tutorial will show you how to switch between Windows Vista users without having to log out.
Switch to another user in Windows Vista
With the regular Vista Start Menu (not "Classic Start Menu"), click on the rightward pointing arrow at the bottom right corner of the Start Menu (next to the Shut Down button and the Lock Computer button), and choose Switch User from the popup menu that opened.
If you are using the Classic Start Menu, go to Start > Shut Down, and Windows Vista will show you the Shut Down Windows dialog box, with a series of choices listed under "What to you want the computer to do?" Click on the dropdown menu, choose Switch User, and click OK:
These two approaches amount exactly to the same thing: here is yet another way to quickly switch user in Windows Vista: hit Ctrl+Alt+Del on your keyboard ("Control, Alt, Delete"), and Windows Vista will display a menu screen, whose second button reads "Switch User": click it.
Logging in as another user
Whichever of these three methods you used, you are now ready to switch user by logging in as another user, or letting someone else logging into Windows. Windows Vista will show you the same logon screen you see when you boot up your computer; it will show a "Logged on" tag below any users (like you) who are currently logged into Windows. Click on the icon of the user you would like to switch to, enter the password, and hit Enter. Windows Vista will log in and load the profile for the corresponding user.
You, on the other hand, are still logged in: to regain control of the computer, you can either ask the other user to "Switch User", as described above, and log back into Windows, or ask them to log off, and then let you log back into Windows. And again, if you try to shut down the computer while other users are still logged in, Windows Vista will notify you before shutting down, and give you the choice to cancel the operation: (just click No, and just log yourself out, leaving the computer on).