I HAVE sony cyber-shot AND WHEN I WANT TO DOWNLOAD MY PICTURE TO MY PC , THE MEMORY STICK WAS EMPTY BUT I SAW THE SIZE AND NUMBERS OF FILES BUT I CANT FIND ANY ?!!

Two options: If you normally transfer your pictures by connecting your camera to your computer, remove the memory stick from the camera before making the connection.

Alternatively, if you use a card reader to transfer the pictures directly from the memory stick, use the "Copy" command in the "Memory Stick Tool" submenu to copy the pictures from the internal memory to the memory stick. The Memory Stick Tool and the Copy command are described in the "Memory Stick Tool" section of the manual (beginning on page 53 in my copy). If you need a manual, you may download a copy from here.

You can see the menu copy the internal memory pictures to memory stick using memory stick commands.If any more doubt watch your manual page number 23

plug memory stick directly with computer through memory card reader and try to recover corrupted files.

Sounds memory stick in your Sony camera is bad or corrupted and requires format.
Use another memory stick.
Or format existing memory stick. format option is available in camera menu.
Let me know exact model number of camera if problem is still there.

Hopefully, Diane, you had the same problem as me. I replaced my memory stick and the
message "no file in this folder" appeared but as soon as I TOOK MY FIRST PICTURE with the
new memory stick, the message disappeared! Good luck!

Many cameras will not let you write to the card. Try using a card reader, which will make the memory card appear to the computer as a separate hard drive.

If you have backed up your files/ fotos, then format the memory stick/ card.

You should format the memory stick. This can be done from your camera.

Have you tried to check the contents of the memory stick from your PC?

If you can't see the files on your PC, there are a number of file recovery software packages available, some are even free.

It sounds like the memory stick would be full why not format it and limit your number of pictures to its capacity.  Download pictures to your PC to have more space.