The Apple Mobile Device Driver is automatically installed with iTunes 7.3 and later versions. This service provides the interface to Apple mobile devices, the iPhone and iTouch. The service should automatically be enabled with the install of iTunes 7.3, however if it has been disabled for any reason (conflict of software), it can easily be started again from a computer's administrative tools.
Click "Start" and then "Control Panel."
Open "Administrative Tools" and then select "Services."
Locate the "Apple Mobile Device" service from the list. Right-click and select "Properties." Click the "Start" button under "Service status." Select "Automatic" under "Startup type."