Error message

I think the problem comes from → wallpaper engine

Did you mean to install a new theme?

Show hidden files and folders
Open THIS-PC
Go to View
Check the box → Hidden items


Go look in PROGRAM FILES (x86)/ Steam \ steamapps \ common \ wallpaper_engineDo you see Wallpaper Engine?

Or look if you see → wallpaper32.exe
C:\Program Files (x86)\Steam\steamapps\common\wallpaper_engine\wallpaper32.exe

If you see it, right-click on wallpaper32.exe and run as administrator

Or check if you see the uninstall program of Steam ...uninstallsteam

Remember to re-hide hidden files and folders

Next we will see if we can disable it at startup in Windows
With the classic method
Right-click on the taskbar → Task Manager
If it does not show up click at the bottom of the window on → More details
Look in the Startup tab
Do you see steam or steam wallpaper engine?

In the Services tab, then search for the service → Wallpaper Engine Service or the steam service
Right-click it and select → Stop

With Revo
Also check Startup entries with Revo
Open Revo
Go to → Tools
Select → Startup Manager
There you look if you see steam
Uncheck the box or boxes
Post a screenshot if needed
Use CJoint here if you want.

You also have a command to access Steam configuration
Keyboard shortcuts Windows + R
Do a copy/paste

steam://flushconfig

then OK

Later we could uninstall Steam in Safe Mode, since processes will be stopped
Do you have Steam games?
If yes back up the folder SteamApps , by copy/paste to the Desktop
But we are not there yet
Or a more radical option would be to Refresh Windows
All settings will be reset to default

Also try changing the theme
Right-click on the Desktop → Personalize
Go to → Theme
Select a theme of your choice

Or go to your image folder then right-click on an image →Set as desktop background
Restart the PC in both cases

--
pistouri

Hello,

Leave Windows default themes, or choose a desktop wallpaper which is safer.
Your Steam folder → WALLPAPER ENGINE must be corrupted one way or another, so the registry key may also be orphaned.

If you want to dare to uninstall Steam, look at this post
It isn’t indicated, but if I were you I would do it in Safe Mode.
Safe Mode is accessible on your PC by going through Settings.
A small explanation here

Otherwise you can close the discussion as this

Have a nice day.

pistouri

While reviewing, I didn’t see it since you said:

I had removed the different programs I had installed including STEAM. Apparently, there must still be files and/or programs left but I can’t find them. 
 

Can you delete what you see in the directory if you don’t get an error message without risk

C:\Program Files (x86)\Steam

Delete the folder → Steam

But also you open the explorer, delete everything and type → steam
it's all or nothing for the search!

Afterwards you can check and delete the registry keys but back them up first with the tutorial here

Back up the Registry manually here

I’m not offering cleaning software for the greater good

You still have to check Autoruns

Good luck...

pistouri