USB drive stuck on read only

Plug the USB drive into any Windows computer.

Navigate to "My Computer" in Windows Explorer (click Start->My Computer[near the top right of the window]).

Right-click on the USB drive:

• Windows 7:
  • Should be listed under "Devices with Removable Storage"
• Windows XP and older:
  • Should just be listed in a list of all drives installed on the computer

Click "Format".

Choose options you want to format as, make sure the "Read Only" button is deselected, and make sure the "Hidden" button is also deselected, and click "OK".

Congratulations! Your USB drive has now been re-formatted. You (should) now be able to format it using Mac OSX.

You can format from a startup disk Read this and try first: http://support.apple.com/kb/ts2176

Or format from the terminal (warning you better know which drive you are working with before you do this) Try this if the first thing doesn't work: https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man8/diskutil.8.html