My 80gb Ipod classic will not work, will not reset and will not be recognised by itunes.

I have a 80gb ipod classic. I was away for two months and didn't use it. When I tried to use it again it came up with a white screen. If i reset it it just keeps the apple logo on the screen. If i plug it into the computer it comes up with a do not disconnect sign on the white screen but is not recognised in itunes. The computer does seem to recognise it as a USB device. None of the directions to put it into disc mode or reset it that i've read seem to work.