Hi all. I joined the forums today if only to thank ytoyoda. After reading his posts from Jan 30Feb 1, and after seeing TekAzurik's success with this approach, I gave it a shot.
ytoyoda's main point is that
the solution is clearing NVRAM
. He also mentions checking for disk errors using Disk Utility. And maybe it was him, or maybe I read it elsewhere, but the general thought was you have to get Boot Camp running and installing Windows after minimally screwing around with your system.
I have the latest and greatest (as of today's date) of the MacBook Pros. This includes the NVIDIA GeForce GT 750M, etc. I had been trying to install a full version of Windows 8.1 Pro via an ISO purchased through Microsoft's online store.
I was using the USB thumb-drive install method but kept getting the "Windows could not update the computer's boot configuration. Installation cannot proceed" message right after the "Installing Updates" completed (before "Finishing up" could begin).
So I gave NVRAM a reset and hoped for the bestbut got the same problem. Then I figured I'd messed with my system and drive enough that it was no longer "pure" and maybe I should just reinstall Mavericks, touch as little as possible, reset the NVRAM and then see what happened.
I booted to the recovery drive. Erased the partition. Used Disk Utility to make sure the drive had no errors (it was fine). Reinstalled Mavericks 10.9.1. I did not configure anything once the OS was up and running. I shut down the system. I did the NVRAM reset. OS X was back up and running again. I started Boot Camp Assistant (the ISO had already been converted to an install set of files along with the downloaded Boot Camp 5.1.5640 from earlier attempts) and the thing worked!
I'd spent a good 12 to 15 hours messing with this thing and finally ytoyoda's thought of trying it on a "new" system worked.
I hope this will work for you all, too.