with the ipod powered off do the following
huck ipod up to PC
hold down home and sleep buttons and count 10 seconds
when you reach ten let go of the sleep button and count 10 - 20 seconds and hopefully iTunes will popup a message saying it's detected an ipod in recovery mode
welcome to DFU mode
the screen on the ipod should look like the ipod has been switched off during the whole time of this process. If the screen turns on to boot up you will need to power the device off and start again