[Closed] I Tunes has made my files invisible!

I've been trying to open individual folders in the i Tunes media folder and the tracks are no longer visible. I know they are there from the properties of the folders and they will play in I Tunes and if I right click on the track in I Tunes and select "view in windows explorer" I can see the mp3 files. However if I just use windows explorer alone, again the folders appear to be empty with the exception in some of album artwork. Some folders do still contain visible mp3 files but the vast majority do not.

Any ideas?