Users are reporting that after installing this week’s Microsoft’s April 2019 Patch Tuesday updates, Windows has suddenly become slow and programs are taking forever to open. The reports we have seen have been from users running Windows 7 and Windows 10. The issues that users are experiencing include Windows taking a long time to start or reboot, lag in games, excessive disk activity, video streaming issues, and other similar problems. A source has been told by a source familiar with the matter, that these issues are being caused by conflicts between the latest Windows updates and antivirus software.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-is-slower-after-april-2019-updates-according-to-users/