I am not sure exactly what ipods this works on i used my ipod classic 80GB so It may or may not on your older ipod.
Step 1: FAST MENU
This is the most usefull if you are a far way from the menu like watching a video or listning to your music.
what you do is press and hold the menu button and you will instantly go to the main menu of the ipod.
Step 2: Enter the Diagnostic Menu
to enter this switch your hold button on then off and hold the center and the menu button untill the apple logo appears then press the |<< button and center to enter the diagnostic menu
Step 3: The End
The end hope you liked it i will add more check back for updates