You Can’t Change The Hardware, So Change Your OS
There are ways to revive older laptops that are too painful to run under Windows, and you don’t need to go full Linux unless you want to. That older CPU and motherboard will run fairly well on an OS with a lighter footprint and that is exactly what Chrome OS Flex specializes in. Bjorn3D has posted a guide to help you on your way to transforming your old laptop into a Chromebook.
For their guide they used a decade old Lenovo B575e, with a Zacate age AMD E2-1800 with a HD 7340 iGPU and 4GB of DDR3. The laptop can technically run Windows 10 once you swap out the original HDD with an SSD, but even with that upgrade it is painfully slow. It does however meet the requirements to run Chrome OS Flex, and though it doesn’t appear on the official list their experiment was successful.