Following this guide includes re-formatting your external USB drive, this will erase the data from your USB drive. If you don’t want to lose the files, make a backup copy first before starting.
1. Open disk Utility on your Mac. (Find it quickly with Spotlight or Finder, click on Magnifying glass and start typing Disk Utility)
You may also open Disk Utility by going to Applications, then to Utilities. Double click on Disk Utility.
2. Select the drive you wish to format from the left side of the Disk Utility window. If you are using the 4GB USB drive which came with the frame, normally, it would say 'No Name'.
3. Click the “Erase” tab in Disk Utility.
4. Select MS-DOS (FAT) from the drop down box beside the word 'Format'.
5. Click Erase and follow the prompts.
6. Select Erase when asked if 'Are you sure you want to erase the disk No Name'.
7. Let it finish, and you are done.