It contains an entry for all files stored on the hard drive that restrains the address of the file’s initial cluster. Corruption of FAT file system primarily occurs due to operating system corruption, improper system shutdown, malicious software like virus and more.This above error message mainly occurs because the FAT file system driver is unable to recognize the two drives and hence the media in your system. As there are various differences between the types of these media, you encounter the above error message. Another major cause for the error message can be physical disk problem or IRP (Input/output Request Packets) corruption.After the FAT file system corruption, the data stored in the hard drive becomes inaccessible. In such situations, if no backup is available, you need to recover the lost data by using efficient Data Recovery Software.