This could be nasty - but first thing to do - is back up what you have have.
Then run a goto a command prompt - and run 'chkdsk /f' without the quotes, it will say something about requiring full access to the disks - and would you like to schedule a chck on next re-boot - say yes, and re-boot the unit.
On the next boot - it will run a check disk on the drives, and this may restore the data to a readable point.
The other thing you 'could try' - but with care (hence backing everything up first_ - is powering down the PC, and disconnecting one of the drives - try each one alternatively, to see if that enables you seeing the files.
Let me know