Can't use apps anymore because I've been elevated to Built-In Administrator

[MikeInPoulsbo]

Don't know how this happened although multiple auto-updates occurred in the last few days. My file associations are all screwed up, in particular photos (JPG file) want to be opened by the "Photos app". Evidently no apps can be opened because of the Built-In Administrator attribute. I've tried to reset that using the suggested commands using the elevated command prompt (net user administrator /active:no ) but that doesn't work. At first I was able to change the file associations for file types I particularly cared about to non-apps and that worked. But yesterday I received an alert that due to some sort of problem (the alert didn't stay on long enough to see what the problem was) the file associations would not be used and sure enough that is what happened. Help!