I think you need to use a partition disk manager. If you download MiniTool partition wizard free 9. http://www.partitionwizard.com/free-partition-manager.html Then run the program and you will see all of your drives. Click on the g or what the sd card drive number is and select the fat32 box. On the left uner operations you should see extend partition. click on extend partition and drag then slider all the way to the right and click ok. Then click apply on the top left and then yes to apply changes. When the resizing is complete you will see the full 64gb on the sd card drive and no unallocated partition.