I gave my sister a Clip+ and she’s returned to me totally frustrated and now I see why. My computer does not recognize that there is anything on the Clip+ when it is full. Meanwhile, I can’t even upgrade the firmware because it’s full. Please, please, please do not tell me to delete song by song on the Clip+. I’ll be up all night. I’ve already tried a new cable and at least now the Clip seems to hold a charge which it did not do before.
You might try, with the player disconnected, changing its USB mode, under Settings, to MSC mode and to MTP mode. With the Clip and a computer, the computer only shows the files that were put on the Clip under the USB mode that the Clip then is connected to the Clip under. A good reason to set to the Clip’s USB mode to MSC mode (the most universal) or MTP mode, and avoinding Auto detect mode in which the computer can flip between the 2 modes, confusing matters when you want to see, from your computer, all the content on the player.
To free the space on your player, you also can easily format the player under the player’s Settings, or via your computer–but note that this will erase all your content.