I was installing Mac OS X Mountain Lion and accidentally shut down the computer while it was updating (MacBook Air). Now, when I turn it on it crashes with the 'You need to restart your computer..." message and at the top says "Unable to find driver for this platform" and Mac OS Version: Not yet set. I tried booting from the Recovery HD, but then it wouldn't let me re-install Lion because it thinks Mountain Lion is installed and it can't downgrade. I went into Disk Utility and backed up the Macintosh HD to an external hard drive, hoping that I wouldn't loose any data. How do I re-install Lion/make my Mac work normally again?? Thanks!