I had a problem recently with an external hard drive holding a large collection of MP3 files. I used File Scavenger to recover the data, apparently very successfully. However, I now find that some of the files refuse to open and media player responds with the message "ClassFactory cannot supply the requested class". This only happens to some files and there is no apparent difference between the good and the bas, both are shown as MP3 files and both are shown as containing the right amount of data. Any advice?