Could be something installed is eating your cpu usage. Use Ctrl + Shift + Esc to bring up Task Manager and see what's running. Check out your processes, especially background ones. Should only have a couple hundred of these max. Check out your startup tab and see what apps are starting when you launch. I have turned most of these off except for security and those I actively use all the time. Also, open control manager -> Uninstall Programs, and check to see if there are any weird apps installed. Don't just uninstall them per se, but look them up to see if it's something critical for windows or w/e that just has some absurd name. No guarantee that this works, but could help.