My pendrive is not working and showing Unknown file System [duplicate]
In most cases what you have to do (I'm assuming you have some version of Windows XP +) is go into CONTROL PANEL > ADMINISTRATOR OPTIONS > COMPUTER MANAGEMENT > Disk Management and then FORMAT the visible drive (usually you might have to delete the partition if something happened to the drive that resulted in corrupt/invalid data). I've had this happen before when formatting a USB to be bootable, it might fail and not mount properly after.
This trick via the management panel, will allow you to manage all your drives. Only formatted drives will show up under MY COMPUTER.
There is a process you can use to format unreadable drives from the command line, I often find it necessary on USB pens that are causing me real headaches.
Open up CMD (open it as administrator if you're running Windows Vista or 7 and UAC) and type the following:
diskpart
In the prompt type in:
list disk
This will present a list of disks, e.g.:
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 149 GB 0 B
Disk 1 Online 7751 MB 0 B
As you can see from the example I have a 150GB disk, disk 0, and an 8GB disk, disk 1, being the USB pen. The next step is completely wipe the USB device:
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
Finally we need to create a primary partition on the disk and format it, in this case as fat32:
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> create partition primary
DiskPart succeeded in creating the specified partition.
DISKPART> format fs=fat32 quick
100 percent completed
DiskPart successfully formatted the volume.
DISKPART> exit
Once you've completed the above steps you should have completely reformatted your USB and it will be ready for use.
N.B. if you get access denied at any point during this process it is likely that you need to run the CMD prompt as admin.