|To enable Windows logon screen, go to start > Control Panel.|
If you are using Windows XP, the control panel menu might come up with a window with a title "Pick a Category." If this is the case, click the link to the very left of the window that says "Switch to Classic View." If the control panel window is already filled with icons rather than links, just ignore that last part.
Once at the icon view, double click on the "User Accounts" icon. The window should now say "Pick a Task..." at the top and there should be a link in the window that says "change the way users log on or off." In that menu, check the box next to "Use the Welcome screen" and then click "apply options."
Close all windows and restart to computer to verify that the fix worked and you should be all set.
Hope this helps!