Why is Music folder empty?

I connected my player to my PC via the standard usb. I dragged & dropped various music files (mp3 format) from my PC to the player. The music is visible on the player & can be listened to also. My PC correctly recognises the player when I connect it but when I open the player’s folders, the Music folder is empty. Is this right or should all the mp3 files i added be visible? Thanks

That’s fixed it, thanks.

Hi, I just purchased a Sansa Clip+ for the first time and was enjoying loading the music files. Seemed to work fine.  Then I made the mistake of updating the firmware. Crikey!  All my files were gone!  Well, only as far as Windows 7 was concerned. I spent ages going round in circles until I came across your solution - brilliant!  I switched to MTP and they’re all back - I can continue loading.  Thanks for your contribution to my sanity.