Wipe the flash drive with a erasing utility then try and format it again. Otherwise look on it if there ain't a switch on the side or somewhere that enables the write protection on it. If there is switch it over and see if it works
1. Shutdown your computer or laptop
2. Insert USB Memory Stick into your laptop or Computer
3. Turn on laptop and then immediately start pressing (F8) key then Advanced Boot Options screen will come up
4. Select Safe Mode with Command Prompt
5. After loading files if your USB Memory Stick drive letter is (G) for example then write as
6. C:\windows\system32>G: and press enter
7. G:\>format G: and press enter
8. If ask you (Y/N) then press (Y) and press enter
9. Now a full format will start which remove write protection from USB Memory Stick.
Before removing USB from your computer, Always remove it safely by going into to my computer then right click on USB and click eject.