2.Type diskpart.exe and press enter
3.Type list disk to see what number your usb drive
4.Type select disk2 (if your usb is disk 2)
5.Type select partition 1
6.Type delete partition
7.Type create partition primary
8.Then if it shows no usuable free extent can be found then
10.Then type create partition primary
11.Then right click the usb and format it.
Note: if you could not go through step 6(cannot not delete partition ) then see if some background process is using the usb or else go in safe mode and try it.