iPod Battery problems

Hi

Can anybody help please?

I have an 80gb black classic 5th generation ipod, it is only just out of warranty (isn't that always the case).

My ipod kept bringing up a symbol of 'battery out of charge' then when I put it on the main, it was playing fine with a full battery.

I was told my my friend, "ah, that must be your internal battery". I bought a battery and fitted it. I don't get anything on the ipod now.

I have charged it up for about 8 hours via mains power - nothing
I have tried the middle button and the menu key - nothing
I have tried the middle button and the play/pause button - nothing
I have tried to refitting the battery in again - nothing
I have tried wiggling the hold button
The computer does not recognise via usb 2

I have even bought another battery just incase it is a dodgy battery - nothing

When I plug the mains in there is a buzzing noise, at a guess the power might be going in?!?

Has anybody got any suggestions to what I should do next or maybe I have missed something?

Missing my ipod

Thanks for your time!!!