update your itunes to new version 10.5
if still not showing put your ipod in dfu mod by holding the power bottom 3 sec then togather power+home botton for 10 sec
then only home botton for 10 sec itunes will recognize your ipod.
check out steps to put your ipod in dfu mode here:
How to put your iphone/ipod Touch in DFU Mode - YouTube
cheers