A computer system will not be able to detect the Walkman NWZ-E435F MP4 if the drivers are not installed correctly. The Walkman NWZ-E435F MP4 is an MTP device and the computer cannot recognize it as an MTP device unless the device drivers for the Walkman are installed properly. A closer look at the hardware devices attached to the computer through the Device Manager utility will reveal all the device drivers installed on the system. From the portable devices section, update the driver for the Walkman NWZ-E435F MP4 and select the Mass Storage Device option during the procedure. Once the drivers are installed correctly, the computer will be able to detect the Walkman NWZ-E435F MP4.