I loaded Carbon on to my phone and Windows 7 PC, to back up files before exchanging my old Nexus 4 for a replacement. Now, my new replacement (also Carbon-ized) is not recognized by the computer unless it is in PTP (camera) mode -- and then, only with USB debugging turned on. I can only see the N4 in my control panel; the Device Manager only lists a generic Android Device with Android ADB drivers. How do I restore everything to original working condition? I have tried turning USB debugging off and on, rebooting all devices and changing USB cables, etc -- nothing works. Suggestions, please. Thanks