This began with my loss of access to an HP 8610 network printer. No matter what I did, I could not regain access. Two other PCs on my home network still access that printer just fine. I uninstalled and reinstalled the printer but still have no ability to print to it. I can even send it a fax and use it to scan, but it refuses to print.
That is where my problem began. Then I tried to update one of the programs that I own, Calibre. When I did, the microsoft installer stopped, first with error 2503 then with 2502. And I said HUH? Same thing happens with a number of other programs. Now, I have been using them and updating them just fine until some time in January. I don't do a lot of printing so it might have been screwed up earlier than mid-January, but that is when I first noticed it.
I run Norton so I did an entire system scan and found nothing. I ran Norton eraser. That found nothing too.
I ran Microsoft Malicious Software Removal Tool. That found nothing.
I enabled the hidden Administrator account in Windows 10. From there, I could update Calibre. The Microsoft Installer seemed to work just fine. (I am testing this problem using this program as Calibre sends an MSI file to do its update.).
This problem appears to be related to permissions but from here I am lost. Any help would be greatly appreciated.