If you can, use an adapter, and insert your card into a pc. Click, and open computer shortcut, look for removable disk ( ), click on icon and open disk. Delete everything on the card. Going back to the computer short cut screen find your removable disk icon again, and right click the icon. click on format, all sd cards and thumb drives are set FAT32 by default. Open drop down list under file system and select NTSF, then start format. This will reformat the card to allow for more files to be stored to the disk. You should always allow the phone to format the card as well for best operation if being used in a cell phone or similar device. Hope this helps, this has help on several occasions for myself and other family members.

If you allow the phone to format the sd card when it is mounted in most phones, you should not have any problems with the card. However there are older phones and mp3 players that will not recognize a class ten memory card and vise versa. A class ten card is not needed for music storage or playback. I simply use a class 4 Micro sd card in my older sansa player. Hope this helps.