Flash CS3 HELP

hi I’am trying to make flash CS3 to save some data from text field to a text file and I found this tutorial http://www.kirupa.com/forum/forumdisplay.php?f=140 my problem is I can’t make it work even if I include the external library #includeSystem.io” when I press CTRL+Enter I got a compiler error stated that “Error opening include file System.IO: File not found.” Is there any other way to save some data from text field into text file?