First try this: If you have never locked it before, try typing in the code 0000. I believe that is default for when you have never edited those preferences. if that doesn't work, You have to connect to iTunes and choose "user's iPod
" or whatever your iPod is called. Then click Restore. This first erases all the contents from the ipod, but not iTunes so you can get you stuff back. The only issue is that if you have any games/apps then you lose the save data and any progress you have made. But restoring your ipod is a safe way to do this when you don't know the password.