Folders turned into files

Hi

I am running a WD 1Tb external drive attached to my PC running Vista Home Premium. A few days ago three folders on the drive started showing as files with no extension. I can no longer open the folders and I have to nominate a program to open the file.

I have run a number of scans on the drive and they have all come back clean.

Can anyone help me change them back into folders?

Thanks

If you are having another computer try to open the folders in the computer.