HP Envy 20 Black Screen On Startup

On Friday, I updated my HP Envy 20 to Windows 10. Once the update was finished my computer started up fine, however, my antivirus software (AVG) said there was an update and I needed to restart. I did so and after the restart and HP logo screen I had a black, but luminescent screen. After a maybe ten minutes of the screen staying like this, I held the power button down to turn the computer off and then restarted it with no problems. I turned it off Friday night normally and it ran normally all day Saturday. Sunday when I turned the computer on the power light came on and I could hear the fans turn on, but the screen remained black. Just black, not even a luminescent black like when I did the antivirus restart. I tried a hard restart like before but nothing changed. I left the computer on like that for around an hour and nothing changed. Figuring it was maybe a heat issue, I opened up the case and dusted the fan and the heat sink but the problem remains. I posted this problem on the HP support board a few days ago and have heard nothing. Any suggestions on what's next?

I last night saw a similar issue on my son's Lenovo B50-30 which I'd recently upgraded to Win10
It appears to be a brightness issue (try turning up the brightness) but bizarrely the brightness up & down hot keys were reversed!!
I've got a gut feeling it'll be related to display drivers but as this was late last night I've not yet given it any time
I'll look this week (perhaps tonight) and will report back if I resolve it

Thanks for the response, robgr, but I think we have seperate issues. My HP is an all in one and there are no buttons to adjust the brightness on the physical unit.

At least I hope we have seperate issue, haha.

Just fixed this, try this
Reverse Brightness Settings on MS Windows 10 - Acer Aspire e15 - Microsoft Community

I just ran the torubleshooter but did need to reboot