Turn off enable disk use Itunes and Ipod

I had a computer crash and bought a new system as part of restoring the library from my Ipod Nano gen2 to my new computer, I was told to put my ipod in disk mode. Now that the library has been restored how do I get my ipod AND Itunes out of disk mode, I have tried to reset the Ipod by pressing and holding the cnter button and the menu button on the Ipod but the check box for enable disk use is greyed out in Itunes