Please, follow these steps:
1. Open command prompt
2. Type the following:
attrib -s -h -r X: /*.* / s / d Then hit "Enter" and wait about 30 seconds
Be careful! Respect the spaces between words and script. Change the letter X with that has been assigned to the USB device on your PC (that you can see it in My Computer. It can be anything, depends on each computer.)
3. Finally, browse the flash drive and delete the "RECYCLER" folder and if there is another one called "Autorun" you have to delete that too.