Change back to old USB-drive

Oké, so I tried Hexxeh's Chromium OS Flow with the help of this Image Writer, but now I want to get it back to the normal format.
But when I try to format it, my 8GB US-drive only points out it has 250Mb...
What do I need to do to completely wipe the image file from my USB-drive, so it can function as a flashdrive with full capacity again?

Kind regards,
Roel