I tried to do this firmware update with MX300 installed in an iMac. The "Superdrive" in the Mac was not functioning correctly, so would neither burn nor boot the firmware CD. I was able to link the iMac to a MacBook with a functioning "Superdrive" via Firewire 800, boot the IMac from the Macbook's Superdrive and perform the Firmware Update. The Macbook was in Target Disk mode and in that mode the iMac could boot from its Superdrive..
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