Why do people have to be so snarky?
It's not that you're wrong: It's that you could be kinder with a probably new-comer to PCs. Even long-time experts can accidentally blow the hardware. I suspect that the attempt to reseat the CPU lead to a discharge that fried either the CPU or the motherboard. Failing the BIOS POST test does have nothing to do with Windows--much more fundamental to the hardware. Time to return the PC to the seller.
But trying to figure out just WHAT a Windows Update affected can be frustrating, especially when the Windows icon appears, then you get the Black Screen. Then the only way to fix it is by powering the PC up and down repeatedly until the blue Recovery screen allows you to start backing stuff out.
But after buying and building and fixing my family's and my PCs and laptops, starting with a PC's Limited in 1985 running DOS 2.x (That was what Dell was before it became Dell) I am frankly tired of, but resigned to the snark. I don't always know the latest and greatest and some things are easier these days, sometimes much is hidden. And MS has, in all of their products, never been particularly logical in navigating the menu pathways to what you need.