Have you tried booting into safe mode with recovery media?
X51 R2 intermitted booting issues
After having this issue for a while, and trying a fresh boot to see if there was "something" else at play, I'm scratching my head about an intermittent problem with the X51 not booting consistently.
I've changed the PSU (existing 330w to new 330w), done a few fresh installs, switched from a DVI to HDMI monitor and cable and run various memory stress tests etc, with no success.
The problem is that about 50% of the time when booting from cold, the Alienware face will appear, then black screen, then the face reappears and the circle of dots (windows 10) goes around a few times, then black screen again and nothing more. Fans continue to whirr, lights are all on, but no mouse trail on screen, nothing, no response to keyboards, disc access appears to continue for a short period. Pressing the power switch powers down the machine more or less instantly at that point. If I leave it powered up for a long time, nothing else happens.
Mostly it runs crash free when in use, though there are occasional crashes.
I'm just wondering how to debug this. I'm fairly happy it's not the OS or drivers given the number of fresh installs, and as it happens at boot it's not likely to be an app crashing.
So I'm thinking it's more likely some intermittent fault with a component - most likely culprit being the the graphics card, which would be an expensive replacement to test.
Does this fault seem consistent with ones anyone else has had? Any suggestions for how to debug this fully?