Have you tried these? Or if you have a digital camera, can it format it for you? Also in the second link below, they are talking about SD card and SDHC, see if that is not ur case.

 http://en.kioskea.net/forum/affich-615112-can-t-format-my-4-gb-micro-sd-memory-card

http://answers.microsoft.com/en-us/windows/forum/windows_vista-hardware/windows-was-unable-to-complete-format-while/cacee343-3253-426f-9c4d-6b4c352aeebc