I only enable CDC class, but it seems the USB is working in composite mode, the composite device in found in device manager on PC. How can I disable the composite mode?
Perhaps, you previously had such device with same Product ID and Vendor ID installed and your Windows PC has remembered that, try uninstalling the device completely and reinstalling it.
On Win 7: Devices and Printers -> right click of mouse on device -> Hardware tab -> device Properties button -> Driver tab -> Uninstall button