Hey with Flex and FlashPlayer 9 it is not possible to save or
change a file (expcept SharedObjects) locally without downloading,
due to security restrictions. With AIR you can. You also can send
data to a server, save the file on the server and then download it
with the FileReference Class.
With the new FlashPlayer 10 you have the abbility to save
files through the FileRefereceClass.