Hi Harsh
If the usual methods do not work for you, try this:
Click your Start Button, then just type cmd
From the resulting list, right click Command Prompt and choose 'Run as Administrator'
Run this command and hit Enter:
diskpart
Run this command and hit Enter:
list disk
(Make note of the disk number you want to wipe and enter it into the next command - replace disknumber)
Run this command and hit Enter:
select disk disknumber
Run this command and hit Enter:
clean
Then close Command Prompt
Open Disk Management (accessible by right clicking your Start Button)
On that USB drive, you should now see it is just unallocated Space, right click that and choose 'New - Simple Volume', accept the defaults and apply that