I have an iPod nano and it seemed to be working fine. After it had half a battery left I decided to charge it on the computer. I put it on a usb port and left it for a couple of hours. When I got back the computer was in sleep mode and the ipod's screen was black. I tried pushing the buttons but it wouldn't turn on. I made sure the key-lock was off and it was. I plugged it back in the computer but it still wouldn't start. I changed two usb ports around and I'm pretty sure its not the cable. I don't want to have to tell my parents I broke it. Please help!

Can you access the battery? If there is a compartment that holds the battery then try removing the battery for about a minute and then try it again. It should reset the machine back to factory start up settings. This same problem can happen in cell phones too.

From Apple's Website:

Reset
To reset your iPod:
1. Toggle the Hold switch on and off. (Slide it to Hold, then turn it off again.)
2. Press and hold the Menu and Center (Select) buttons simultaneously until the Apple logo appears, about 6 to 10 seconds. You may need to repeat this step.

Tip:
If you are having difficulty resetting your iPod, set it on a flat surface. Make sure the finger pressing the Select button is not touching any part of the click wheel. Also make sure that you are pressing the Menu button toward the outside of the click wheel, and not near the center.
If the above steps did not work, try connecting iPod to a power adapter and plug the power adapter into an electrical outlet, or connect iPod to your computer. Make sure the computer is turned on and isn't set to go to sleep