Unseen files

My mp3 player is a Philips GoGear Aria. I'm not sure what version it is.
There are music files that appear on the screen of the mp3 player but do not appear on Windows (v7) or on MP3tag v2.5. Why is that?
What can I do to make those files appear on my PC? I have the latest version of the software available from Philips loaded.
Any help or suggestions would be appreciated.
Thank you.

You do know that this is the MP3tag forum, don't you?
MP3tag can only edit files that are recognized by the underlying OS - which is windows.
If your player does not allow Windows to access these files then there is hardly any way to get any further with Windows based programs.
How do you know that the files are actually on the player? Or could it be that they are referenced in a playlist but because the playlist does not match the files list they cannot be be played?
How do you access the files on the player?
Are there other files that can be "seen" by Windows? What type are they and what type are those that cannot be seen?
Do you have the explorer set so that it shows also hidden files?