I have tried over a dozen times to install Slow Ring 15048 on top of my 15002. It goes through all the steps, but then when I finally reboot I have 15002.
I've run SFC /scannow - no errors.
I've run DISM /Online /Cleanup-image /RestoreHealth and it fails with error 0x800f081f
(from what I read online, it says to download an image of the ISO of 15002, and use the Sources switch, but I can't find that - the links into Microsoft.com provided in the forum I read it in no longer work, and they weren't insider preview editions anyway).
I've tried booting in safe mode with networking, but my video card displays a black page after Windows boots (the BIOS setup and boot manager screens are fine). I tried to manually set my resolution to 800x600 and then reboot in safe mode with networking, and I get the same result.
I have two GeForce GTX 980Ti's that are SLI'd. Somewhere I read that the problem is that NVIDIA uses the actual opengl.dll, but Microsoft Windows 10 uses some stripped down opengl.dll. I've tried to move my displayport to multiple other sockets on the back of my computer, but the monitor gets no signal. (I don't recall how to set up the UEFI to ignore the graphics cards and just use OnBoard graphics). I haven't tried pulling the graphics cards because that is a four hour project just to attempt.
I tried Clean Boot; I disabled all non-Microsoft services and disabled all startup's. Still didn't work. My anti-virus (3rd party) wouldn't allow it's services to be disabled, so I uninstalled it. Still didn't work.
What does it take to upgrade? Why doesn't the upgrade process tell me "this isn't going to work"? Where can I find a log that tells me why 15048 doesn't boot? No errors are reported to me.