Why is my computer slower after reinstalling my operating system to fix an issue with blue screens?

Answer 1

When rebooting, press F2. When in setup, scroll down to onboard devices click enter then down to flash cache module should say enabled turn that off then scroll up to sata operation and choose ATA then exit and save and try to reboot this worked for me. At worst case scenario, you can always change it back.

Another answer:

When you reinstall the operating system, you likely won't have all of the drivers. Microsoft supplies some default drivers to get the machine to work at all, but they likely won't recognize features specific to your machine. So you would need to make sure you have all the manufacturers' drivers installed. For instance, the default video driver will likely only give you limited colors and slow graphics, with only software support for DirectX, and no acceleration. So you'd need the video driver from the manufacturer to unlock its features and improve its performance. There are also motherboard or "platform" drivers, storage device drivers, etc., and they may need to be installed to improve performance.

Also, once you reinstall the OS, you will likely need to tweak it again. Windows enables a lot of options to improve appearance by default. So if you don't need animated dialog icons, font smoothing, mouse smoothing, and other things of that sort, you can disable them and increase the perception of speed.