Hi,
I had the same problem with my Nano. However after many suggested attempts to start it up, I finally worked it out. I connected it to my laptop with the white cord, pressed menu button for about 20 seconds and finally it responded. It wasn't the music that was important because Itunes have stored all of my music. It was the short videos of my dear little granddaughter whom I have no more, that was most important to me. If the motherboard hasn't failed, and if it is just a case of having not used your old ipod for a long time (because you have probably bought a new one, or an IPhone) connect it to your computer. Wait until you see the Apple Logo, press onto the Menu button for about 20 seconds, and hopefully it will respond.