W10 hangs prior to login screen

I can tell half of the problem in one word "Upgrade"! You upgraded the previous build to the 10240 and are now running into the all seen too often upgrade goobers! Those can either be immediate where you know something went wrong or wait a bit to appear after some time rather suddenly.

You actually could see a repair install following the guide for that without a full clean install or simply end up dumping the upgrade entirely to resolve this type of issue once and for all by going completely fresh! Still being a new almost equal to how the 7 RC wsa when that came out 10 still needs to see a number of updates that will tend to correct some of the errors being seen. There won't be any more SP1s to worry about waiting for but some large update packs put together over time as one came out at the beginning of the month.

Besides the Disk Check tool's "dskchk /f" switch you can also try it with the "/r" switch as the alternative. F=Fix R=Repair Since you have already run the SFC your other option again still points to the upgrade to repair type of install vs a full clean install.
Upgrade to Repair type install guide: Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums[2]=Installation%20and%20Setup
Full Fresh Clean Install guide: Windows 10 - Clean Install - Windows 10 Forums[2]=Installation%20and%20Setup

You'll notice that the same are seen in my signature there since a readily available reference is needed since so many will be having some type of "Upgrade Blues"! And when nothing seems to work eventually besides the repair options you have to break down and call it day saying: "Yup it's that time again!" where you simply make your preps for backing things up and then go for the gusto!

Once I dumped the original upgrade in favor of the full clean install here after that first week 10 has been running along side 7 as if it had been on all the time 7 has been! No headaches to report well still getting accustomed to the three versions newer features as well as changes in GUI mostly!

When booted live you still have the option to upgrade but will still end up with a need to reinstall any number of programs especially those that require internet connection for activation status as well as the program's link for updates and other things. When looking at the clean install guide one of the screen will show the two options for an Upgrade or the Clean install option right under that. So you're totally out of the loop there at least once you have the media prepared unless the Reset PC option is used.



For a VM project you wouldn't be able to use the upgrade option in most situations as to why that is Xed out there. And while booted up in Windows you won't see the "Custom (advanced)" option for seeing a clean install take place however since the set up will simply roll on only seeing the necessary prompt screens come up generally during the final stages for selecting location, type of network, setting up pc name and the admin account.

In years past with the Legacy upto XP you could see a custom install take place by running the installer while in Windows not to upgrade over the version you were booted in but could set up a Windows install on another partition or drive. That was one old method for setting up a dual boot. Since that time however you either boot live for a clean install if not seeing an upgrade or start things up manually with the setup.exe file found on the media while booted in Windows and see the set up process exit the desktop and restart the system a few times as things go along.

One thing urks me a bit about 10 hanging on you right before arriving at the desktop. During the several failed upgrade attempts here on the main build later finding that additional drives lacking any OS had to be disconnected the few times the system was restarted and seemed to be progressing past the logo screen you were suddenly confronted with a dark blank screen not jet black however but seemingly lacking any vga signal. Have you made any type of hardware changes since 10 first went on by chance?

Before arriving to the last resort type of conclusion I had to ask about that since with 10 it seems tto only take one thing being awkward to gum up the works. Up until this time I could always leave the storage drives plugged when not always leaving things that way however and still see each OS drive end up with a stand alone install on them. With 10 however the rules seem to have changed a bit.

Well that's an interesting twist there! Here the primary is on the left side as it would be in most cases for dual display set ups. With a 3rd monitor something evidently made an adjustment likely when not having used the 3rd monitor for some time and then suddenly boot into the developer build with it turned resulted in it being detected as the primary automatically since the onboard will always override the expansion card!

What will happen is often the onboard will take resources used by the expansion for it's own use leaving the card looking for a substitute as well as Windows adjusting to the change automatically seeing the onboard as the Number #1. Generally it would be advised when wanting to add onto any dual display set up to see a second video card put to use and never enable the onboard as that can clash. Some boards even went as far as seeing SLI Quad options for running four separate identical video cards one card per display on higher end gaming machines.

The slides themselves wouldn't have any effect on display settings other then Windows managing how they will be viewed. Here I can add on a 3rd display by simply adding in the same model card if still found and plug in the 24" flat screen tv close by. But the present version of UltraMon in use would likely need to be upgraded or another program that supports a 3rd display would need to be found in order to keep the same basic configuration while allowing the 3rd to mirror the primary or secondary if the option is available with the program selected. That part would be software controlled.

Try this: press and hold down the power button. Twice.
This may or may not solve your problem, but it is worth a shot. My issue seemed similar.
I had about 60% of battery life left, put my Windows 10 Dell laptop to sleep with a new power adapter plugged in. (It had been upgraded from Windows 7.)
It didn't boot the next day.
I turned it on and off repeatedly but never reached the login screen.
Blogs all said the same thing: restart it multiple times and Recovery will save your ass, if all else fails reinstall, etc. But when the Recovery screen didn't appear, like the awol emergency broadcast system that was nowhere in sight during 911, I tensed up.
Mine wasn't such a dire catastrophe.
I pressed the power button again but mashed and held it down in frustration. Click.
It pretended to power up then stopped.
I repeated it.
It came up, saying updates were being installed. That must be why it hung up, but it had not given any indication that it was updating the night before. So if yours hangs like this, return the favor: give it the finger. You'll both feel better.
P.S. Upon booting I noted the battery was fully charged, so it wasn't the fault of my hardware in my opinion. Something like this used to cause desktop machines to lock up in olden days, and the quick fix was the same. Good luck.