Recently I purchased two SD cards preloaded with Raspbian from Adafruit. Each card is 4 GB in size, and is class 4 in speed. However, they both came write-protected, preventing formatting in both Windows and Ubuntu. In Ubuntu the card appeared as two or three partitions, and in Windows it appeared as if the card only had 55 MB of total space. It seems it occurs when certain software with write-protection is used to create the contents of the card, and so the protections can only be removed with that software (but not really).
The solution was to follow this guide (and also possibly to put tape around the write-protection slider on the side of the SD Card):
And now the whole card is visible.