A long time ago on Windows 10 I had the option to set my lock screen to use the Windows Pandora app album art. I can’t remember where this setting was originally but after working for a little while, it appeared to have gotten stuck and I had had the Arctic Monkeys’ Fluorescent Adolescent as my lock screen and sign-in screen background for probably near a decade. The image was at a terrible resolution for use on a 1080p monitor, let alone 1440p, and I only just now decided I may as well fix this.
Getting Rid Of The Old Image
Setting a new folder for a lock/sign-in screen background would work… mostly. Locking the PC would for the first couple of seconds actually continue to show me the FA album cover! After a few seconds it would actually use the correct slide show. Going to the sign-in screen from the lock screen would bring back the album cover as the background.
Clearly, just using the Settings to change the images was leaving some old files and values somewhere, and maybe that’s why it all broke in the first place. I started to search online for other instances of similar issues and spent some time digging through various registry entries to see if I could find any settings that looked relevant or hopefully ones that looked like they might have been set by Pandora and not changed by the Settings screen. My first success was finding the folder C:\ProgramData\Microsoft\Windows\SystemData\{Some sort of long ID}\ReadOnly\ which had some folders named LockScreen_F and others with different letters at the end with background images stored inside. These were in fact a bunch of old album covers that Pandora must have placed, including the Fluorescent Adolescent one.
N.B. The folder is owned by SYSTEM so to clear out old images I had to take ownership of the folder and Windows will attempt to change the owner back to SYSTEM on this folder at various times so its a bit of a pain. Without taking ownership by default no other user can even read the contents of this folder.
I was able to delete the folders and this did remove the phantom old lock screen and sign-in screen backgrounds.
But Now A Different Problem
However, it now appeared it could not use any lock screen or sign-in screen images, and changing things in Settings didn’t appear to apply. Choosing a new image for the lock screen would cause the preview to just have a loading spinner and a blank gray background and the actual lock screen just had a flat black background. Choosing a folder for a slideshow would have the same effect and after a while a warning would appear that “Getting these images is taking longer than expected”. The actual lock screen would once again eventually change to using the correct images for the slide show (this time starting with the blank black image) and the sign in screen would remain blank.
I eventually found another post online discussing the registry keys under HKCU/Software\Microsoft\Windows\CurrentVersion\Lock Screen and this was the first time I actually found a reference to the fact that Pandora had been involved. I made a backup of this registry folder and attempted to remove the references in the registry here to Pandora as well as what looked like references to the various lettered folders and images that I found in the SystemData folder. Unfortunately this still didn’t change the black image being used. I still could not even set a single image for the non-slideshow option in Settings.
At this point I had a suspicion that maybe I had removed too much and so I went looking for various registry keys and folder names that I knew I had deleted hoping people were posting about them. originalfile was one of these registry keys I had deleted and seen referenced in a search or two for people trying to fix their Windows Spotlight (that app from Microsoft that changes the lock screen and wallpapers daily). Some searching later, I found someone who was using an external program to set their wallpaper and they wanted the same image used for the wallpaper to also be used for the lock screen and sign-in screen. They were able to get it working by creating a hard link to the file that their program updated to set the wallpaper inside the C:\ProgramData\Microsoft\Windows\SystemData\{Some sort of long ID}\ReadOnly\ folder by replacing one of the files in a folder with their hard link. I decided to try recreating the ReadOnly folder and then using Settings to select a single image for the lock screen, and the preview actually loaded the image! It turns out deleting that folder must have been breaking the Settings panel and recreating it allowed it to create the needed subfolder and place the images inside. (Microsoft, I know you tried to save me from myself but Im surprised that the Settings app didn’t recreate that ReadOnly folder).
And now I can finally enjoy all my Okami wallpapers even on the lock screen!
Extra Bit
Turns out that by default the lock screen slideshow does more than just rotate through images. It actually has some sort of built-in “make a collage looking thing” every so many slides with a bunch of the images cropped and combined. The registry key to control this wasn’t present but I found a post describing it and it has the most ridiculous format I’ve seen. They chose to use a DWORD (32-bit number) instead of a string and so when the dev has to build up the slideshow schedule you do the obvious thing and n%10, then n/10, but the order is reversed from what you expect.