iPod classic 160GB wont turn on and wont even charge?

I have an Ipod classic 160gb the thick version and when its not plugged into the computer or the wall charger it wont turn on, but when i plug it into the computer or wall charger all that comes on the screen is a picture of a battery with an orange triangle with an exclamation mark in side it saying "Charging, Please Wait...

I have let it charge for 12 hours and its still showing the same picture and the battery in the picture is still in the red but as soon as i take it off the charger or off the computer the screen goes blank and it wont turn on. I have let it charge, i made sure the hold button was off, i have tried to reset it and nothing has worked. I was going to try and restore it but the computer wont even read it or notice its connected. HELP!!!! what do I need to do???????