Disable right-click on the Taskbar

Paste the following in notepad and save it with a '.reg' extension.

Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer] "NoTrayContextMenu"=dword:00000001

Merge it with the registry.

To allow right-clicking on the taskbar delete the "NoTrayContextMenu" key from the registry.