1. Open Elevated command prompt

2. Type: diskpart ENTER

3. Type: list disk (find your usb disk number) ENTER

4. Type: select disk 1 ENTER (Where 1 is put your USB drive number.)

5. Type: attributes disk set readonly ENTER

To Remove use steps 1-4

5. Type: attributes disk clear readonly ENTER

Remove flash drive and plug it back in. It can write again.