Classic British Flight Sim

Just about had it with Steam.

It claims FSX was running. It wasn't
It would not allow me to refresh Steam Cache because FSX is running - it's not.
It would not allow deletion of FSX - it's running - it's not
It would not permit deletion of Steam itself - FSX is running. It's not.
I delete Steam thru' the Windows Control Panel. Success except for C:\Program Files (x86)\Steam\GameOverlayRenderer.dll and log
Defrag C & D drives.
Reboot just in case
I attempt to reinstall Steam - it cannot the directory is not empty C:\Program Files (x86)\Steam
Grrrr

Check 'C:\Program Files (x86)\Steam' and if there are any files/folders in there right-click on them and select 'Properties'.

Check to see if any are marked 'read only'.

Remove any check marks for 'read only' then try to delete the files/folders.

Marking files as 'read only' will prevent them from being deleted which might be happening in your case.

I tried a repair and thought to hell with it and backed up what I could and carefully removed P3D4, I did the take W10 back to its start thing. A pain having to go thru' all the re-install shenanigans but in some ways it makes for a cleaner machine.