Windows 7 has the in build feature to set it to automatically log on without having to enter the password. If you have customized the Windows 7 taskbar, then when you restart your PC having enabled the automatically log on feature, the customizations made to the Taskbar are lost and the Taskbar is reset to its default settings. Microsoft has mentioned that this problem occurs because of a race condition between Windows Explorer and Taskhost.exe.
Microsoft has released a hotfix for this issue and it is intended to correct only the problem that is described above.
To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. You can get in touch with MSFT support by using this link
This fix applies to Windows 7 Enterprise, Ultimate and Professional versions along with Windows Server 2008 R2 versions.
More details available here.