Neets: I wanted to put the stock Optus firmware back on my phone after gaining the 3BR mode.
I've followed the instructions from XDA:
In the steps, after connecting the phone via USB it says to wait for the drivers to be installed before clicking the START button in Odin.
My phone is sitting in the Download mode, it's connected to my computer, but I don't see any drivers installing.
How do I get out of Download mode?
If Windows doesn't show the driver progress dialog then it already had the drivers installed (or it did it very quickly!). If you want to check look in Device Manager when the phone is connected by USB in download mode, under "Modems" you should see "Samsung Mobile Modem".
When you start Odin you should see one of the boxes under ID:COM go yellow and contain e.g. "0:[COM19]", which is the COM port of the phone in download mode.
To get out of download mode just hold the power button in until it resets, or take out the battery (it's OK to do this if the download hasn't started).