Is your usb flash drive or sd card is corrupted or whe you plag in a computer it says usb need to format and when you format it say windows is unable to format the disk then here I suggest a possible solutions to repair your usb or sd card drive
Now I'm going to show you how to repair your usb flash drive or sd card
There are three different methods
Method one is by using command line and method two is by using disk manager and method three is by using windows Explorer
>>METHOD ONE
BY USING COMMAND LINE
In this method we will clean and format the disk using command prompt
PROCEDURES
.Plug you flash drive or sd card in your computer
.Click the start windows button and type "cmd" in search box and hit enter then the command prompt will open
.In the command prompt type "diskpart" without space and hit enter.
.Now type "list disk" and hit enter.Then the list of disk will be displayed and choose the disk that you want to repair
.Then type "select disk 1" if your disk is disk 1 and hit enter
.Type "clean" and the successful message will appear that say the disk part is successful in cleaning the disk
.Type "select disk 1" and hit enter
.Then type "create partition primary" and hit enter
.Now type "active" and hit enter
.Now type "select partition 1" and hit enter
.Now type format fs = fat 32 and hit enter then wait until the progress to complete (100%)
.Enjoy with your repaired flash disk or sd card 
>>METHOD TWO
BY USING DISK MANAGER
IN this method we format the disk using Disk manager
PROCEDURES
.Right click on my computer icon if you are using windows xp,7, 8 or right click on this pc icon if you are using windows 8.1, or 10 and select manege
.Now select disk manager an wait until the list of disk is appeared
.Right click on the disk that you want to repair and click format
.Wait until the progress is finished. If you have good lack then your flash or sd card will be repaired 
>>METHOD THREE
BY WINDOWS EXPLORER
PROCEDURES
.Open windows Explorer and right click on the usb or sd card that you want to repair and click format
.Now in the popup window make sure you not tick on quick format and click ok.
.Wait until is finished.It will take a few minutes then quick format so be patient
Enjoy to use your usb or sd card
Chapisha Maoni