Credit : http://raspberrypi.stackexchange.com/questions/1446/how-can-i-reformat-my-sd-card-to-use-it-normally-again Start a command prompt, and start the DISKPART console. List all of your disks by typing LIST DISK , then select the proper disk with SELECT DISK # (where # is obviously the SD card). You can then type CLEAN (MAKE SURE YOU SELECTED THE PROPER DISK!), and it will clear the partition table on the card. 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 ASSIGN . If you're unable to determine the proper disk, remove the SD card, run DISKPART and LIST DISK , and then re-run it with the SD card inserted. The SD card is just the disk that has been added.