If the memory stick itself doesn't show up on your computer, try rebooting the computer (with the memory stick unplugged) and then plugging it in again. Sometimes something as simple as that will work. Or try another USB port (ensuring that you use a port directly on your PC, not via a hub).
If the memory stick shows up, but appears to be empty then (after checking that you've actually plugged in the correct memory stick!), try this:
http://download.cnet....-2242_4-10753287.html
In either case it might also be worth trying the memory stick with a different computer.
Chris