Sounds like some part of the cooling system has failed if it is overheating just when generally browsing and no heavy processing apps or graphics running. You could try a laptop fan unit that blows air under the laptop and raises it to allow better airflow (available on the Bay of Fleas). however you then have a device tied to a desk. I had an all-in-one and it got continually slower, even after taking it apart, vacuuming and air-blowing and removing lots of dust. It could also be that you don't have enough RAM. No matter what Microsoft says, Windows 10 needs 8MB if the whole machine is to run easily, I purchased 16MB to make my more future proof and because I run multiple browsers and graphics apps for mapping.