If after upgrading to Windows 10 you can’t change your display brightness (the option may be missing in Settings/Display), this may be your fix.
- Right-Click the Start button and select Device Manager
- Expand the Monitors section
- Right-click on Generic PnP Monitor and click on Enable
After fighting to find the latest video drivers (HP hasn’t re990leased Win 10 drivers for my Pavilion), this fixed my issue.