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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.

Credit: http://brucesbraindump.blogspot.com/2013/04/removing-raspberry-pi-partitions-from.html C:\temp>diskpart Microsoft DiskPart version 6.1.7601 Copyright (C) 1999-2008 Microsoft Corporation. On computer: PC014033 DISKPART> list disk   Disk ###  Status         Size     Free     Dyn  Gpt   --------  -------------  -------  -------  ---  ---   Disk 0    Online          167 GB      0 B   Disk 1    Online         7460 MB  5802 MB MAKE SURE YOU SELECT THE CORRECT DISK OR YOU WILL WIPE THE WRONG ONE !!! DISKPART> select disk 1 Disk 1 is now the selected disk. DISKPART> list part   Partition ###  Type              Size     Offset   -------------  ----------------  -------  -------   Partition 1   ...