MP3 player locked up, won't play, can't turn off

From off, when turned on, displays name of the 1 book in memory and total time. Can't play, advance to different chapters, or turn off. Must remove battery to turn off. When connected to computer, displays "USB" and book plays from the beginning on the computer in Win Media Player. So, access to memory is possible with WMP. Tried "remove hardware safely" routine, didn't solve problem. Win explorer can read the memory, shows the 1 book loaded, and 2 other "system" type files.
Thanks for your help.