Since I keep doing this for one Windows computer after another, here goes. Microsoft “helpfully” advertises the Windows 10 upgrade by installing a tray icon for Windows 7 and 8 users through Windows Update. It is annoying and it steals CPU cycles, so let’s get rid of it. There is a good explanation here, but in summary uninstall KB3035583 and then mark the update as hidden.
To uninstall from an administrator command prompt:
wusa /uninstall /kb:3035583