Why doesnt itunes pop up when i plug in my ipod to the computer?

when i plug in my ipod to my brothers laptop, i can see the ipod on itunes, and itunes pops up when i plug in the ipod, but when i use my desktop computer itunes doesnt pop up and i cant see or my ipod icon on the side to where io can add music. how do i change it so it can show on my desktop? thanks!