In Windows, if your Start button and Taskbar seem to be missing, try moving the mouse to the very bottom edge of the screen. The Taskbar should pop up. If it does not, try moving the mouse to the top edge, the right edge, and the left edge. The Taskbar should appear on one of the edges.
To stop the Taskbar from disappearing, right-click a portion of the Taskbar without any buttons, or the clock portion of the Taskbar, and select Properties. It's likely that the Auto hide box is checked. Uncheck it.
In Windows XP and Vista, to stop the Taskbar from being moved to a different edge of the screen, right-click a portion of the Taskbar without any buttons, or the clock portion of the Taskbar, and select Lock the Taskbar.
If the Taskbar...