I'm having a real headache trying to reformat a USB drive. Initially it had a 200mb EFI partition and it caused the drive to disappear altogether. Since then I ran the CMD and wiped the disk using 'diskpart'. It took a few attempts but it finally cleaned the drive.

Since then it has reappeared under (:E) however I am unable to access the drive and Windows is preventing me from reformatting it. I am just presented with 'Windows was unable to complete the format'. It's now acting like a CD drive instead of removable storage.

I've tried going through Disk Management and I'm presented with the same error. I've removed the USB controllers from Device Manager - when the drive is connected again it re-installs the drivers and acts the same way.

Any help given will be greatly appreciated, thank you.

(Windows 7 machine)