External hard drive "corrupted or unreadable"

I have been using a 500gb Buffalo Drivestation external hard drive to store videos and music for the past several months without incident. However, two days ago when I tried to access the drive in Windows Explorer, the program appeared to freeze. This happened repeatedly, including following system reboots and unplugging/plugging in the hard drive.

When I finally allowed Windows Explorer to 'do it's thing' without ending the process, it informed me that "the file or folder is corrupted or unreadable." If at all possible, I would like a solution to this problem that will allow me to access the data that is on the hard drive at least long enough to copy it to another disk. Although most of the data is backed up, there is some that is not.

In Disk Manager, the drive appears as usual. However, when I tried to run chkdsk I received a message saying that "The root folder on this volume is full". I know for a fact that there is over 200gb of free space on the drive. Chkdsk also said "Error writing folder".

Also, I have tried accessing the drive in another computer - with the same result.

Any help you could give would be much appreciated. Thanks very much!

 

As an additional point... Disk Management says that the file system on the external hard drive is RAW, while Checkdisk recognises it as FAT32.

 

So you have obviously run chkdsk /r on the drive?