Go on to your itune software and get it started. Connect your ipod nano to your computer. Once the software recognizes the ipod look for the setting that indicates that it is in disk mode. It should be close to the bottom of the screen and uncheck the selection.
You have to switch that in Itunes, not on the actual I pod. If you go into the settings of the Ipod in I tunes, the screen where you can see the amount of space is on your ipod, there's a small box that says enable disk mode. If you un-check it, it will take care of your issue.
You will need to reset your Ipod Nano by holding down the menu and center keys for A few seconds. The Ipod Nano will resume normal mode once it reboots.
You need to reset your ipod nano. Hold down the menu button and the middle button at the same time for 10 seconds or longer until you see the screen shut off. Let go of the buttons and the ipod will reboot and then it should work normally.