The F5 key turns the backlight on and off. I think in order to use the F keys for their usual functions you have to press another key too, like the fn key but I have not tried that yet. Pressing the keys on their own does the things pictured on them instead, like keyboard light, volume and mute, and stuff like that.
I have not really noticed the difference between it and my old smaller laptop when carrying it around. I have one of those padded laptop bags for it and it is much lighter than my pack full of books for school most days.
It is an excellent desktop replacement laptop for its price. It has plenty of processing power and better than usual sound so it is good for games that do not push the video too hard. Unfortunately it uses the CPU chipset video (an integrated Intel® HD Graphics 4600) which is very good as far as imbedded 3D video goes but I am not sure it is up to the cutting edge 3D performance needed by some of the newer high-end games. I do not think it has a slot to install a third party card but I could be wrong about that.
the processor is quad core and currently the battery cannot be upgraded to a 9 cell battery because it is not yet available to my understanding. I checked a hp battery chart for all their notebook models and under the envy 17 series it shows a 6 cell and 9 cell battery for that model. The battery probably just hasn't come out yet, so keep checking periodically until it does.
Go to Control Panel, Devices and Printers, Mouse. A window opens showing tabs. Click on the right one "Click Pad Settings" and check the box "Disable internal pointing Device." I tested it on mine and it apparently works. Other HP forum responses say it cannot be done.