DO NOT DO THIS!!!
He doesn’t know what he’s talking about. I’ve actually done this before and the reason he gives for it overheating is wrong and his fix is temporary at best. The factory “defect” isn’t in the heat dissipation, it’s in the solder itself and BIOS settings. The stock heatsink is more than sufficient to dissipate the heat, the problem is that the factory BIOS doesn’t properly increase the fanspeed and the GPU overheats. If people used the HP updater (no one ever does) you’d have gotten the updated BIOS and never had a problem.
Using a blow torch is stupid and will likely do more damage than the overheating did. The reason the GPU stops working is because nVidia used weak solder and the GPU actually unseats from the motherboard. It’s not much but even a tiny fraction of an inch is enough to cause issues. The majority of the time, just heating the chip up will not be sufficient to fix it. You need to heat the chip up using a a heat shield similar to what was in the video and a SOFT heat source like a hair-dryer (which re-loosens the weak solder) and then apply pressure to force it back down into the socket. Press gently for about 30 seconds (using a towel or thick gloves to prevent burns) then let the chip cool for 5-10 minutes. After that attach the power, ram, and screen and see if you get the HP logo, note that you do NOT need to re-attach the heatsink to do a POST test if the chips are at room temperature. If you don’t get the logo, try again, if you do get it clean the stock heatsink out and reattach it. Be sure to apply thermalpaste to both chips.
Also worth noting, this solution does not fix vertical/horizontal lines on your screen. That’s caused by either a dying screen or permanently damaged GPU.