Google Power Tools Bible
Closing the Google Talk window does not close the application. It continues to run, which is indicated by a Google Talk icon (a red M in a speech bubble) in your computer’s taskbar. To re-launch the Google Talk window, double-click on the icon in the taskbar.
To close Google Talk completely so that the application no longer runs on your computer, right-click the icon and select Exit from the pop-up menu. To restart Google Talk, start the application from you computer’s Start menu. Select All Programs