If the Taskbar is reset to the default settings when you use the “Automatically Log On” feature in Windows 7 and in Windows Server 2008 R2, then you may want to apply this hotfix KB 979155.
You configure a computer that is running Windows 7 or Windows Server 2008 R2 to automatically log on when you start the computer. When you restart the computer, any customizations that you made to the Taskbar are lost and the Taskbar is reset to its default settings.
This problem occurs because of a race condition between Windows Explorer and Taskhost.exe.
To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix.
More at KB979155.