The File Allocation Table, or FAT, is perhaps the most widely used file system on personal computers, recognized by Windows, Linux distributions and Mac OS. It's most commonly used on solid state storage devices like SD cards and USB flash drives.
Attach the flash drive, memory unit, or FAT-formatted hard drive to the PC. Go to "Start," then "My Computer" to determine what drive letter the device is assigned.
Go to "Start," then "Run," then type "cmd" (without the quotes) and press "OK." The command prompt will open. Type "C:" (without quotes), then click "Enter" to make sure you're on the drive that contains Windows.
Type "chkdsk y: /x /r" (without quotes), where "y" is the drive letter assigned to the device. The /x parameter dismounts the drive to prevent it being accessed while scanned and the /r parameter searches for and recovers damaged sectors. Press "Enter."
The chkdsk utility may be used to fix problems with the FAT file system, but doesn't necessarily recover data. This might also be necessary if the FAT can't be fixed and needs to be formatted. See the Resources section for recovery tools.
You can add the parameter "/fixmbr" to the chkdsk command if the FAT device is meant to be a bootable device.