It's not unusual for hotkeys and such to stop working if you have upgraded the OS or are otherwise not using the original video driver. You should still be able to adjust the screen brightness in the BIOS though. For example there is only one Windows 10 driver for your HD4250 and it supports neither Control Panel nor Catalyst Control Center.
However from the mention of Aero you may still be running the Windows 7 that laptop shipped with. In that case it sounds like you haven't installed the correct driver and are running on the generic Microsoft Basic Display Adapter driver. To fix this, simply go to support.hp.com and download the video driver for your laptop and OS. Once that's installed (and perhaps also the Quick Launch keyboard driver), your problem should be fixed.