I use my HTC 8525 running Windows Mobile 6 to listen to music that I’ve saved on a 2gb storage card. Yesterday I loaded up Media Player on the phone and discovered that all of the music had disappeared! Nothing I could do in Media Player would bring the music back, it was all missing except for a few music files that I had stored in the phone itself. I tried re-inserting the card and Media Player detected it but still the music did not show up.
After trying a bunch of things unsuccessfully I finally found out that using the file explorer on the phone I could browse to the storage card and delete the folder called MSMETADATA. This is a hidden folder so in order to see it in File Explorer select Menu and then check the “Show All Files” menu item. Once you delete that folder, reload Media Player, and rescan the card by selecting “Update Library” from the menu. All of your music should reappear in Media Player.