After much waiting and tribulation, I've finally successfully unlocked tethering and installed Paranoid Android on my Nexus 7 3G device.
In the progress, I had to tell Windows to ignore its default MTP drivers and use Google's debugging own to interface with Android, fastboot and the like. As a result, I now can't go back to accessing the device using MTP from inside Windows itself.
I tried uninstalling all the relevant drivers from Device Management, but now Windows prefers Android ADB Interface to whatever I was using before. I've tried to force the setup of MTP drivers from Device Management, Add legacy hardware, Install the hardware that I manually select from a list, Portable Devices, (Standard MTP Device), MTP USB device. This didn't work ("This device cannot start. (Code 10)").
How can I get file transfer back?