Firstly, in order to fix the issue, reboot your computer and your iPod Touch. After that, check if you have the latest version of iTunes installed on the PC and make sure that your device trust the computer. Next, go to Start > Control Panel > Uninstall a program/Add or Remove Programs feature and check if Apple Mobile Device Support is installed. If it is not installed, remove iTunes, QuickTime, Apple Software Update, Apple Application Support, and then reinstall iTunes. Restart the Apple Mobile Device Service (AMDS) and check if the device is recognized. If it is not recognized, visit Apple support page for further solution.