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Q: I have a Samsung 16GB SD HC Micro card that was formerly used in a dash cam. It contains several directories that start with a period (see included graphic) but even those that do not are not erasable. None of the videos on the disk can be viewed (“corrupt file” error). I want to repurpose the SD card but cannot format it. I have tried all the usual stuff and even downloaded a partition manager that said it would format anything but nothing seems to work. I’ve tried the Microsoft suggested CMD prompt to do it and even that doesn’t work. Any suggestions on how to completely reformat the disk?

 – Fred W.
Shalimar, Florida

A: I have a few suggestions for you, Fred.  Whether they will work for you or not will depend on some information that you inadvertently left-out of your question.  No matter, we’ll step through it bit by bit, and I hope I hit on the solution for you.

I want to first say that despite their role as data mass-storage devices, flash devices – particularly “removable” ones – are unique, and should not always be handled like you would with say, a hard drive.  Many, if not most of the device access commands intended for hard drives will work on SD cards, thumb drives, etc., but not all of them.  Now, it’s not entirely clear to me if you’re using an SD card adapter to connect the card to your computer.  That’s important because SD cards (and adapters) can be write-protected with a mechanical switch on the side, and a write-protected card could account for your inability to format it.  If you’re using such a device, look for this switch, slide it to the other position, and try your format again.

As you probably already know, Windows does not allow you to start a filename or folder name with a dot.  But these files were not created by Windows – they were created by the dash cam.  That device’s manufacturer is apparently using dots in filenames as a method to protect the files in Windows.  You won’t be able to access them or delete them, because Windows can’t handle filenames that begin with a dot.  The only exception to that rule are entries named “.” and “..” that you’ll find in every folder of any device except that device’s root.  The single dot essentially means “this folder”, while the double dot means “this folder’s parent”.  In my opinion, these are most useful when writing batch file scripts that need to traverse folder hierarchies to process groups of files, but I’m sure there are other uses for them.

In theory, as long as the device isn’t write-protected, a standard format command should be able to recover the space on the drive and make even a corrupted device usable again.  I wish you had told me the exact error message you’re getting rather than just “cannot format it” and “doesn’t work.”  Do you know the type of file system implemented on the card?  If it’s anything other than NTFS (New Technology File System) or FAT32 (File Allocation Table – 32 bit) that could cause a problem, but not one so monumental that it can’t be overcome by using the FORMAT command with the Quick Format option turned off, or the partition manager you said you tried.

There’s one thing we haven’t talked about yet, and that’s the one thing we know can format that particular SD card.  I’m talking about the dash cam that you took it out of.  Despite their size, these devices have a tiny, highly limited operating system built in that allows them to perform all the necessary functions of writing and deleting files.  In every case I’ve ever seen, they also have the ability to format media, to prep it for use in the device.  I suggest you fire up that old dash cam, insert this media, and see what you can accomplish.  Once the dash cam has had a chance to clean it up, remove old or corrupt files, or even format it altogether, perhaps you’ll have better luck reformatting it on a PC.