My Sansa clip+ won't turn on what so ever

SanDisk MP3 players Sansa® Clip | Sansa® Clip+
59

I kept getting a message to say that my sansa clip was full. (even though it isn’t) and now it won’t even turn on.  I have held the on button down for 20secs.  And also it is not registering with the computer even though my drivers are up to date.

Any ideas.

Regards

Jan minnis