Sadly, you can't password-protect an entire folder, just individual files, so I suggest you do that. You could also "Hide" the folder (right-click, properties) but this will only be at all effective if you run Windows with "Show hidden files and folders" turned off. Personally, I think a flash drive is much more liable to be lost or stolen than a laptop, unless you have one specifically for sensitive data and keep it locked up when not in use. If your old computer no longer boots up, it's not really safe to rely on it for keeping your files! Good luck!