How to Move the Task Bar & Start Menu Back to the Bottom
In Windows 7 and Vista, you can move the taskbar and Start menu to any of the four corners of your screen---the top, bottom, left or right. Wherever you decide to move your taskbar is a matter of personal preference. By default, the taskbar is usually on the bottom of your screen. However, if you had previously moved it to any of the other corners, you can restore it to its default location.
Right-click the taskbar from the location you have it and click the "Lock the taskbar" option to uncheck it. Since the taskbar is not on the bottom of your screen, it should be on the top, left or right of your screen.
Click any part of your taskbar, hold down the left-click, and then drag the taskbar to the bottom of your screen.
Right-click the taskbar again and click "Lock the taskbar."