Computer won't read iPod

My iPod won't connect to the computer, i plug the usb cord into my ipod and the my computer, but the computer wont read it, this isnt my first time plugging it in, i always charge my ipod and sync songss off of this computer, so i dont know why its not working now and i dont know if this helps at all but recently i attatched my ipod to a surround sound system to play it, and now i cant get it to work on the computer