A couple of things to try.
plug in your Ipod and but it in Disk Mode: Reset by holding Menu/Middle buttons, then hold Middle/Play until disk mode appears.
Leave it plugged in.
1- Go to Control Panel
2- Open "System"
3- Click "Hardware" tab and click "Device Manager"
4- Find and maximize "Universal Serial Bus controllers"
5- Right click "Apple Mobile Device USB Driver". Click "Uninstall" (If it's not installed, get it with Itunes.)
6- If it doesn't all work out right there, unplug, replug you Ipod and you should be good.
Look here, click here