Close Media Player go to.... -My Computer --> C: --> Documents and Settings.... Here, double click the name of the supervisor/administrator/user (eg. David) --> Local Settings (If local settings is not there....go...Tools -> Folder Options -> View -> Show hidden files and folders(tick the box)) --> Application Data --> Microsoft --> Media Player. here right click on each of the three files, in turn, which end in .wmdb and add .bak to the end of the file and confirm. so for example the bottom one should be called wmpfolders.wmdb.bak. After doing all three, close the window and run Media Player. the library should work now please let me know if this works or doesn't work!