If inserting a corrupted Micro SD Card, that you need to recover data from, freezes your computer, then this kind of puts you into a catch 22 situation. For recovery software to work the card needs to be detected and ID correctly. As long as it doesn’t you will be unable to recover your data. A common observed symptom is the computer starts functioning normally as soon as you remove the card.
Corrupted Micro SD Card
As far as Windows is concerned a Micro SD Card is just another storage device. So, as soon as it detects it, it will start a process called ‘mounting’. In order to mount a drive it will read all kinds of meta data from the drive, and this meta data starting point is the very first sector. Any bad sector in the meta data Windows is trying to access will cause the process to hang indefinitely.
In many cases if the drive is connected via USB (such as a card reader connected to the USB port), eventually Windows will disconnect it. If you’d happen to be observing Disk Management you’d simply see it disappear.
From a data recovery perspective this auto mounting procedure is highly undesired!
What not to do
Many file recovery software related websites (RecoverIt, Stellar, DiskDrill) address the issue, however often they come up with moronic tips and advice. These include running chkdsk which you can’t because the drive was never mounted, or perform destructive actions using DiskPart.
On the other end of the spectrum are the chip-off cowboys. These are labs who paint the worst possible picture and explain how they will recover your data using expensive chip-off or direct NAND dumping type recovery methods. Now there are cases where this is indeed the only way to recover the data, but as far as I am concerned it’s the last resort option as it is labor intensive and therefor expensive.
The DIY Method (some risk involved)
You can tell Windows to not mount removable devices. To do so open an administrative Command prompt. Type DiskPart and press enter. Then type automount disable and press enter. Reboot and try inserting the corrupt SD Card. Run file recovery software (my goto recommendation is ReclaiMe) to recover the files if the card is showing up in Disk Management with correct capacity.
Or send to an inexpensive data recovery service
By this I do not mean a PC repair shop. You need to send it to someone who professionally deals with data recovery! I mean a smaller independent yet professional lab (e.g. avoid DriveSavers, Ontrack, LC Tech and similar).
Chances are that running a DIY file recovery tool will choke on the bad sectors too. There is also the real chance it will make things even worse! An inexpensive, independent lab or data recovery service will first of all take precautions to not worsen the condition of the drive. First of all they’ll prevent Windows from mounting the drive using special hardware. These tools also can get the SD Card to ID very often when Windows can’t, thus allowing them to clone the drive. Cloning is also controlled by hardware to prevent further deterioration of the the memory card.
I offer this service myself for as little as $59.95, which is less expensive than purchasing a good file recovery tool. I am in Europe, the Netherlands so sending me your card from a different continent may be impractical (but very do-able my experience tells me).
If this method however fails, the only remaining option is the more expensive method of dumping the contents of the NAND chips and re-assembling a logical image from this raw data. This is a complex process as all tasks normally performed by the controller (correcting reads using ECC, translating physical blocks to logical sectors, descrambling of data) need to be configured and emulated by software.
If you want to get some idea of what’s involved for example watch: