Portable USB flash drives have become the most frequently used storage devices and, at the same time, the big annoyances when they fail. When connected to a computer such bad flash drives can be identified as "unknown device" or have RAW format or can be seen in the system as a disk with a zero capacity. If you try to access them the messages like "Insert disk" or "no disk access" can drive you completely mad.
Occasionally, a flash drive becomes read-only and when you are trying to create/delete a file the "Disk is write protected” message occurs. This message is a strong indication of the firmware damage, so controller on the flash drive switches to protect the data to prevent NAND from further deterioration (memory of the NAND flash is damaged mainly in the course of data record).
Are you wonder of all these terms: controller, NAND, etc? OK, then just a piece of theory.
Any flash drive has two basic chips: controller and NAND memory. Controller is responsible for transferring data between a computer and NAND memory and is managed by the firmware. Part of the firmware (memory settings, the compiler, various IDs and flags, etc.) is written in the memory chip. In the case of various power failures, bad data recovery and other reasons this firmware may fail. As a result, the controller is locked and not responding to requests of the operating system. Also, blocking may occur as a result of the memory wearing or when a threshold of write cycles is exceeded. In this case, controller itself marks a block as unused and blocks record to the NAND memory.
We assume you are a tech-savvy and know how to recover flash drive … but if you don’t know and want to repair flash drive for free then follow some advice:
First, recover the functionality of the flash drive’s controller. To do this find utility to work with it. If you know both the controller model and the name of the flash drive manufacture then a suitable tool can be found on the manufacturer's website or somewhere else on the Web. If you are unaware of the controller model use controller’s VID and PID codes to find it. For example, VID = 13FE and PID = 1D00 are relevant to PHISON controller. To find VID and PID for your flash drive use the specialized utility such as CheckUDisk 5.0. You can also look up the VID/PID (vendor/product ID) in the registry under HKLM\SYSTEM\CurrentControlSet\Enum\USB. However, the registry key does not always indicate the manufacturer, and rarely the chipset. (There is a companies database that lists VID and PID against company names and type of controller they used on specific flash drive. This list changes almost daily.) Viable for determining PID, VID and type of controller for your flash drive is ChipGenius tool.
Common usb flash drive troubleshooting
After the recovery of the flash drive’s controller it is very likely that you will be able to get at least some data from the NAND memory chip. The best known utilities to do it are R-Studio and PhotoRec.. The last one is distributed for free by its developer.