You probably have a hidden file on your memory stick called autorun.inf
Delete this file.
You might also have a virus recently as viruses some times use the autorun file to spread therefore you might want to run a virus scan.
Once the file is deleted remove the memory stick and then reinsert.
Delete this file.
You might also have a virus recently as viruses some times use the autorun file to spread therefore you might want to run a virus scan.
Once the file is deleted remove the memory stick and then reinsert.