While testing the Enterprise Edition upgrade for Windows 8.1 I received the following error message:
We couldn’t install Windows 8.1. We’ve set your PC back to the way it was right before you stared installing Windows 8.1.
Error code: 0x800705AA – 0x2000C
I was using Hyper-V with dynamic memory set at 512MB. During certain phases of the upgrade 512MB isn’t enough memory. The recommended amount for the upgrade is 2GB.
See KB2878739 for more details.