Remember to backup all your personal files from your TAC Drive. Open the Utilities folder:



Run Disk Utility:



In the right pane, select the volume under the TAC Drive usb hardware:
(If the volume has been removed, selecting the TAC Drive itself will work, but you might have to eject and reinsert for the volume label to update correctly.)



Select the Erase tab in the right pane:



Select FAT in the format dropdown, and ensure the volume name is TACDRIVE.
(If it offers FAT16 vs FAT32: FAT16 is acceptable for 1 or 2-Gibibyte TAC Drives, but FAT32 is ideal.)



Press the Erase button and confirm.
The process might take a few minutes.