IMPORTANT=     Make sure you are the administrator of the PC

1. Make sure you have itunes installed (easy way to make sure you have the drivers for your ipod)

2. try using a different USB port, some ports are only enabled for input devices like keyboard and mouse.
     other usb ports could be disabled in the BIOS. so make sure you use a port you know works for your printer or camera etc..

3. Restart your PC, it will rescan for hardware changes, or go into device manager and hit the scan for hardware changes button.

if you're still having issues then you might want to check using your ipod on a different pc, maybe the culprit is the cable you're using!.