Sandisk cruzer 16GB became read-only

No your device comes from the factory in the Fat32 format. You can just insert it into the usb port of your computer and start copying files. I have determined with a lot of research into the same problem for me and a lot of tweaking of the registry, also using the disk management tool, the command prompt to format it that way, that it is a hopeless situation. With the SanDisk formatted in Fat32 you can only place 4 gigs of files on it. Here is the rub: Since I have the same identical problem, I have concluded that (without any advise from Sandisk) that I should have immediately upon inserting the device, began a reformat to the NTFS format. Then the device can accept more than the 4gigs maximum and you can add files at your leasure almost up to the 12 or so gigs left for writing to. I did’nt do that, so I concluded that after loading my files and removing the disk, the built in file structure of the SanDisk told it (in the Fat32 format) To lock up the system so that no more files can be added. I still have the 2.7 gigs files that I can read, but I can’t write to them. I can also copy files back to My Documents, but as far as reformatting the disk, forget it. You should have reformatted the disk to NTFS immediately upon insertion. I know this is not a helpful answer, but it seems to be a reality.