Last night I was working on my USB drive and then removed that USB from my computer and went to bed, Today ,morning I started my work from where I had left last night, I had formatted the USB which I was using and got socked because my USB was of 4 GB last night but now its just of 1 GB.
Then I quickly launched my Disk Management Tool and I was completely shocked, There was almost 2 GB of space was unallocated.
As space was unallocated so I think lets allocate it and everything will be OK, but I got another shock, as I right click on it, every thing was greyed out.
So I goggle a bit and finally got a simple to use tool, SdFormatter, which allows you to format any of your USB, like Pen Drive, Memory Cards and so on.
Then you need to select the drive which you wanna format and then just click on Format button and you are done.