After downloading Windows 10, my internet speed went significantly down, from 35 mbps to 4 mbps. I recovered my original Windows 8.1, hoping it was the new Windows that was causing the problem, but my computer is still very slow compared to what it used to be. I know the problem is in my computer because the three other PC's in my house are all working at normal speeds. I ran a virus scan with no luck. Could the Windows 10 upgrade have installed something that's still slowing down my internet? Any help is appreciated.