+the registry settings used by the itunes drivers for importning and burning cds and dvds. this can happen as a result of installing other cd buring software. please reinstall itunes+
With that one, try a reboot and repair of iTunes.
Reboot the PC (very important) and then do a repair install of iTunes. In Vista, go "Start > Control Panel", and (if you're in the Control Panel Home view), click "uninstall a program". Select iTunes, and click "Repair".
If no joy there, check for a device filter conflict, as per:
iTunes for Windows: Troubleshooting CD issues caused by device filters