Mac OS X 10.6: If items automatically open when you log in
Applications or documents may be configured to open automatically whenever you start up or log in. Some software installation programs add applications or documents that open automatically.
To temporarily prevent items from opening when you log in:
If the login window appears when you start up your computer, hold down the Shift key while you click the Log In button. Continue to hold down the Shift key until you see the Dock.
If you don’t see the login window when you start up your computer, hold down the Shift key when you see the progress bar in the startup window. Continue holding down the key until your desktop appears and the startup completely finishes.
To permanently prevent items from opening at login:
Choose Apple menu > System Preferences, and then click Accounts.
Click Login Items.
Select any items you don’t want to open automatically, and then click the Delete (-) button.