Audio files missing

Question

I have a Sylvania SMP1015 MP3 player. I plug it in and transfer files to it using Windows Media Player. It seems to work fine and I get no errors. All files (188) transfer. When I unplug the player from my computer The player only shows 55 files. I plug the player back into the computer and I am able to view the files (all 188) thru both the Windows Media Player and thru Explorer. I have also tried playing the files to insure that the missing files were not corupt or unplayable and all the files are good.