You have to find out what program its associated with and stop it from running. Icons only appear there for programs that are running.
Try clicking or right-clicking on the icon and selecting some task that causes it to open up a window. When it has a window open, find the window in the "Applications" tab of Task Manager (Ctrl + Shift + Esc), right click on it, and select "Go To Process". That'll tell you the name of the program.