I've had problems with two 8GB sticks (different brands) after they were messed up by OsX, I managed to format them and restore them (diskpart) but I could never get Win7 USB/DVD Tool working with them again. Only method that would work in creating a bootable stick was with diskpart, as mentioned in post #5. Low level format just takes too much time imo.
I always use HDD LLF Low Level Format Tool in quick wipe mode, then i use these cmds to setup the usb stick. Diskpart List disk Select disk ? Clean Create partition primary Select partition 1 Active Format fs=ntfs quick Exit