Go to C:\Users\<your account>\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar
Go to C: \Program Files (x86)\Diablo III
Delete "Diablo III" and "Diablo III Launcher"
Left click the pinned icon on your task bar.
Choose "Delete"
Go to Recycle Bin and restore "Diablo III" and "Diablo III Launcher"