How can I reformat my SD card to use it normally again using command line (windows)?

Start administrator's command prompt: 

a). Open start menu

b). Type cmd

c). Right click and run as administrator or Press Ctrl+Shift+Enter

d). Enter diskpart to fire up the utility called diskpart. Literally, enter diskpart command.



DISKPART> prompt should appear.

Now in diskpart prompt type: LIST DISK and it will list all your Disks including your USB drive. Note the Disk number.

DISKPART> LIST DISK


Type the SELECT DISK <num>, where <num> is your USB disk number. Just look for right capacity of the drive.

DISKPART> SELECT DISK <num>


List all partitions on it: LIST PARTITION. (Just for verification)

DISKPART>LIST PARTITION

Clean the partitions using CLEAN Command

DISKPART>CLEAN

CREATE PARTITION PRIMARY - To create PRIMARY partition manually

DISKPART>CREATE PARTITION PRIMARY

FORMAT FS=FAT32 QUICK - You could use NTFS instead too.

DISKPART>FORMAT FS=FAT32 QUICK

ASSIGN to assign character to drive

DISKPART>ASSIGN

That's it!
Close the command prompt and use the SD card as normal.