By default, the Yahoo! Messenger starts when Windows does. If you don’t use Yahoo! Messenger regularly, you are wasting resources by having it run when you don’t need it. To stop Yahoo! Messenger from starting when Windows does:
1. Open Yahoo! Messenger.
2. Click Messenger and select Preferences.
3. Select General from the left pane.
4. Under When I start up my computer, uncheck the Automatically start Yahoo! Messenger checkbox.
5. Click OK.