Dear Thelma et al,
You probably withdrew your storage device before it had finished transferring material.   Put it back into THE LAST COMPUTER YOU USE iT ON  -  after about 30 seconds, ask the computer if it is safe to remove the device by clicking the green arrow in the sys tray =  bottom right hand side.   Do this three or four times - DO NOT RUSH THE PROCEDURE.  It worked for me.  Good luck.
Brian Murray.
                
 Brian Murray
                
 June 2006