All you have to do is:
- Connect the iPod to your PC using a USB cord.
- Open iTunes.
- Click the Options button in the lower right corner of the iTunes window.
- Click Enable USB disk use. (sometimes optional)
- Go to “My Computer” and select your iPod.
- Select tools and the folder option.
- Select the “view” tab.
- Select “Show hidden files and folders”.
- Search for the file (file name differs in earlier versions) but on all models it will be located in the “Ipod_Control” folder aka Settings
- Look in a folder that is sometimes called “Device” find a file named “_locked”.
- Change the file name “_locked” to “_unlocked”.
Sometimes you dont have to go into itunes but can start straight from step 5