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.
if your pendrive is transcend made then use their utility like "OnLineRecovery" with internet connection... this stupid problems only occurs in transcend pendrives ( i think, because i have faced this )