Important Download Info for Macintosh OS Customers If you currently have only Mac OS9 on your system, you will not be able to download and install the electronic version of Norton™ Personal Firewall for Macintosh® 3.0 on your computer. Please select physical shipment as your delivery method instead. We apologize for any inconvenience. If you currently have both Mac OS9 and Mac OSX on your computer, you can purchase the downloadable version now.