This experience may be useful to others.
I have just encountered an extraordinary range of issues (not all at once thankfully!), including screen freeze, inoperable dvd drive, black screen with fan operating continuously and, finally, a complete refusal to boot.
I tried removing the battery and running off the mains electricity to see if the battery was causing a power fluctuation. Conversely, I unplugged the mains adapter and tried running on battery power only. I also ran the HP PC Hardware Diagnostics UEFI to test the main components on my computer. Despite trying everything I could think of (I'm not a technician!), the problems just compounded until nothing could be done.
My suspicion is that there may be a power circuitry issue on the motherboard. Perhaps, someone more knowledgable can confirm this?
Fortunately, this 6-month old laptop is still under warranty and has been sent away for repair.