I have a Sansa e280 and I had the same problem with accessing the MUSIC directory under FILES.
I too also wanted the songs to continuously play from one artist to the next under a certain genre type. However, according the manual, this can only be done with songs accessed from the FILES directory and NOT the DATABASE directory. (I wish they would change this so it would work in both directories. It would make life a lot easier.)
I downloaded the manual and found the answer in there. Here's how to get MUSIC to appear under the FILES directory:
Go to:
-Settings
-General Settings
-File View
-Show Files
Then select "ALL"
Afterwhich, re-boot the player. Your music should now continuously play from one song to the next under the folder name you choose.
HELPFUL HINT: I purposely organized all my music into folders by Genre (Pop, 80's Music, Dance Music, etc). This works kinda like a playlist when using FILES to access your music.
I also changed the genre in the MP3 song itself by going into the properties of the file and changing the genre to match the same title of the folder that it's in.
The only downfall is if you want to listen to a particular artist like, let's say, Michael Jackson and he's in the 70's Music folder, 80's Music folder and the 90's music folder. You would need to go to each folder to listen to them. OR simply create a Michael Jackson folder and put all his music into there.
Does this help you?