Hi, welcome to TSF
Paint.net attempts to update itself automatically every time you run it, so maybe they've upgraded some part of the update feature, and it now needs a newer version of Windows Installer. Or it could be that there's a problem with your Windows system files that is causing some kind of conflict.
Download Windows Installer 4.5.
Install and reboot, then try installing Paint.net again.
Paint.net attempts to update itself automatically every time you run it, so maybe they've upgraded some part of the update feature, and it now needs a newer version of Windows Installer. Or it could be that there's a problem with your Windows system files that is causing some kind of conflict.
Download Windows Installer 4.5.
Install and reboot, then try installing Paint.net again.