Unfortunately, I have KB4284835 installed and I am still unable to access the new "Set defaults by app" interface.

For reference, the model is identified by the sticker in the bottom right of your second photo: "AG3850" means that this is a Radeon HD 3850 using the AGP slot interface and "512MDR3" means it uses...

I can't even use edge. Every site I try to go to gives me the generic "Hmm, we can't reach this page." error. Never really had much of a need to troubleshoot it, since I'm quite happy with Firefox.

I'm going to stick with AVG (I generally prefer this over Avast) and Malwarebytes.