Usually the windows 8-8.1 product key is tied to the motherboard and all you would need to do is down load windows 8.1 from Microsoft and do a clean install CLICK HERE for instructions. Sometimes the product key is behind the batter if it's removable.
You say you have had problems with drivers not working properly in windows 10. Have you ever been to the laptop Manufacture web site to check if they have updated drivers available? I have found on some laptops you have to manually install drivers from the Manufacturer web site for some things to work correctly.
Have you tried doing a clean install of Windows 10? CLICK HERE for instructions (Your Windows 10 will have a digital licence and will reactivate when connected to the web)