"Corrupt" directory in MP3 player

I have a portable MP3 player and can't find a brand-name mentioned anywhere in the packaging, but it's the flat cigar shaped type of player that is currently very common at the cheaper end of the market. I get a message saying "The file or directory is corrupt or unreadable "
I have put all music into a folder of that name, and, until yesterday, I was able to add new tracks or remove them from my PC, but as of this morning, my home PC and now my PC at work cannot access the Music folder.
I can still play the tracks on the player, and can delete them using the MP3 controls, but cannot access this folder on a PC. I can load new tracks or material into what little space remains on the root directory, but when I try to play these on the player, I get an hourglass icon for about 30 seconds, and the player then switches itself off.
given that the MP3 player does still play, isthere anything I can do to remedy the PC folder access problem?

 

Ok. Problem sorted. I re-formated the player and now all is well. I shan't bother creating folders in future.