SD flash memory cards are convenient for portable data storage and moving data from one computer to another. They are also commonly used in digital cameras to store pictures and to make them easily transportable to computers and printers. Occasionally, you may find that you cannot access the data on a card. This can range from mildly annoying to catastrophic.
Note that there is no guarantee that you can retrieve your data from your card. If the card is physically or electronically damaged, it may not be repairable. But here are some things to try if you can’t access your data from an SD card.
Determine the type of SD card you have. If it is 2GB or less, then it is a standard SD card. If it is 4GB or greater, then it is a high capacity or SDHC card. (There are some 4GB standard SD cards but most are SDHC). An SDHC reader is required to read the high capacity cards since the memory allocation formatting is different. If your data is on an SDHC card, it may be intact but you'll need the SDHC device to read it. Some devices, such as readers and cameras, may have software downloads available to upgrade the device to read the SDHC cards. Go to the device manufacturer's website to determine whether such an upgrade is available.
Insert your SD card into the card reader. If no drive letter is assigned to it, then the computer isn't reading it. In some cases, the reader may be assigned a drive letter but when you click on it you get the message "Please insert disk into drive E:" indicating that it isn't reading the card.Sometimes a particular device may not read an SD card while other devices will. If you don't have another device, ask a friend to try reading your card.
You may find that your computer accesses the card, but won't read the files on it. Try several different files on the card. If some of them read and some don't, then one or more files may be corrupt. There are numerous file recovery programs available; some of them are free. If certain vital parts of the file are corrupted it won't be recoverable. Sometimes scanning the SD card will fix things. It usually won't correct a bad file but it may be worth a try. To do this, locate the card in "My Computer" or Windows Explorer" and right-click on it. From the pop-up menu, click on "Properties." A new window showing a pie chart displays the used and available space on the disk. Select the "Tools" tab, then click on the "Error Checking" button. Click the check box for fixing file system errors and click the "Start" button. The process should only take a few seconds.
In some cases, none of the files can be read. Sometimes the directory will list the file names but the files can't be accessed. In other cases, the file names are garbage characters or they may not show up at all. Right-click on the drive letter and select "Properties." The pie chart will show the used space on the card. If it shows all or almost all free space, then either the files have been deleted or the directory has been erased. In this case, a file recovery or undelete program may help (but don't count on it).
If you card reads okay but you can't save a file, the card may be write protected. On the edge of the card is a small slide switch usually labeled "Lock." If this switch is slid away from the connector end of the card, then it is "locked" or write protected. To save or modify files on the card, the switch must be in the unlocked position or toward the connector end of the card.
If you still can't read or write to the card, your files are probably lost. There are some disk diagnostic tools available, but some of them won't work on memory cards. If you have resigned yourself to the loss of your files, you may still use the card by reformatting it. To do so, right-click on the drive letter and select the format. This will erase everything on the card so be sure you have copied everything you can to another drive. When the card is reformatted the directory structure is recreated so you should now have full access to the card. If the card still won't work, it's time to discard it.