Installing the props upside down will NOT reverse the thrust (i.e. 'drive the model into the ground'), it will just make them less efficient (I've been an aeromodeller for over 30 years, and this is a common misconception).
I have only just received my Phantom and have yet to unpack it so I'm new to this game.
But if you go to the Phantom FAQ's on the DJI web site under 'Software Problems - Why my Windows 7 OS cannot install the assistant drive successfully?' You will see that you may need the userser.sys file...