Raw filesystem
When you plug in (for example) your external USB drive you get the error: Raw filesystem, or the pc doenst recognize it all.
You do the following:
Open commandprompt (start -> command -> rightmouse button ->run as administrator)
typ in:
chkdsk F: (example) /f
# If your driveletter is E: do:
chksdk E: /f
This will scan and fix your disk!