Why can't I install my antivirus software?

Rick upgraded to Windows 10 and now he can't install his AVG antivirus software. It keeps telling him there's another installation in progress. Rebooting doesn't help. Leo says that it sounds like the Windows installation program may have gotten corrupted. He can fix it by resetting the MSI Exec file. HowtoGeek.com has an article on how to do this.

Leo also says that AVG may be an issue as well and there's no reason to use it now that Windows has it's own antivirus with Windows Defender. So he should just enable what he already has and ditch AVG.