Start a command prompt as administrator.
Enter DISKPART at the console. List all of your disks by typing
LIST DISK, then select the proper disk with
SELECT DISK # (where # is the SD card). You can then type
CLEAN to clear the partition table on the card, effectively blanking it. MAKE SURE YOU SELECTED THE PROPER DISK BEFORE RUNNING THE
To create a primary partition to reuse the space on the card, type
CREATE PARTITION PRIMARY. This will then reallocate the previously “cleaned” space.
To format, type
FORMAT FS=FAT32 QUICK, and finally, to reassign a drive letter, type