I'm making progress and am extremely grateful to you as you have single handedly led me down the right path to at least recover all of my data.I believe your USB external drive may be drawing lots of power from the Surface; faster than the battery can charge. So it is a good idea to use that car charger for now.
For a cold boot (also called a "Two-button reset", do this:
You are making progress! Keep at it ...
- Press and hold the power button for 30 seconds.
- After Surface turns off, press and hold volume-up button and the power button at the same time, for at least 15 seconds (The screen may flash the Surface logo before 15 seconds, but don’t release the buttons).
- After you release the buttons, wait for 10 seconds.
- Press and release the power button again, and your Surface will be turned on again.
I've tried the "cold boot" but that procedure somehow just brings up the UEFI screen. You did, however, say "Have you tried a cold boot (via UEFI screen)?" So is there something I should be doing on the UEFI screen?
I'm now at the stage where I can operate windows without it cutting out (but using power saving mode). It still cuts out when you remove the power though, even in safe mode.
One other problem is that I can't switch the wifi on and the little icon at the bottom of the screen has a red cross on it. I've checked device manager and Marvell AVASTAR Network Controller is missing. I'm thinking it might be possible that the hardware has been damaged as it was in the repair shop for 3 days and the guy said that he "made an attempt to take the screen off but something was sticking". I've read that it's the wireless adaptor that gets in the way when you are carrying out this process so that's fairly ominous!
I've also now rolled the surface back as far as it will go and all of these problems are still occurring.
Do you think it's time to format the machine and put a fresh install on? I've backed up all of my files so no problem there. My only worry is that the battery won't be able to handle it (although it was happy to be in safe mode for a long long time so maybe it will be fine). I could still put it in the freezer too if that will help! Nothing to lose now I have my files back!!