Check whether this helps.
1. Shutdown your computer
2.Plug-in your USB drive
3. Switch on the computer and get into safe mode by pressing F8 key.
4. In the Advanced Boot Options, select Safe Mode with Command Prompt
5. If your USB drive letter is D then C:\windows\system32>D: [ENTER]
6. D:\>format D: [ENTER]
7. If asked (Y/N), press (Y) [ENTER]
Now a full format will be done hopefully removing write protection from the USB drive.