Unknow files (blank files) in Media Player 11 List

This files Can't access and Can't delete (if you selected all and remove all this file still be there)

simply solution is because Windows Media cache files

For vista
Goto

Local Disck > Users > XXX (Your User Name)>AppData>Local>Microsoft>Media Player

Delete All *.wmdb for manual reset cache Windows Media files

Now Go back to your Windows Media Player and see problem Unkonw files are gone