I have a sansa e250 and i have 400 and something songs they all used to play. now only a few of them play what happened

Freezing up while playing songs Check and see if there is a boot file in any of the folders on the player use the Explorer to check Check both MTP and MSC modes and unhook your player
Delete songs and Format (Helps with try to delete BAD TRACKS and folders that will not delete(Some ripped CD folders).. Go to my computer scroll to sansa or your MP3 player and open the music folder and open each sub folder and delete Songs manually then delete the folders them selfs then format a couple of times hope this works