Protecting taskbar from changes

Open Registry and navigate to "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\policies\Explorer". Now click on edit->new->DWORD-Value and create an entry with the name "LockTaskbar". Double click on it and set the value to "1". This will disable the context menu "Lock the Taskbar". To enable it, just change the value to "0" again.