So it appears that Adobe Flash has been removed, but I'm unable to delete the folders from my drive. Each folder (and included files) were created by "TrustedInstaller" and cannot be removed, even by an Admin of the system. I tried taking ownership of the files and folders, only to be greeted by the same error message, except that MY admin account needed access to the folders.
Had the same issue - after hours of banging my head against the wall - I think I did it. There is probably a much easier way but I could not find it (I do not trust the old "download this super powerful free uninstaller tips). Anyway.
I found all the folders and had the same response - not able to delete which freaked me out - I mean hey get rid of Flash due to security issues but then you cannot get rid of these folders or files from my own computer - suspect to say the least. That is why I took the time to find this.
First I ran the adobe uninstaller - which as you found - did NOT actually remove everything.
Note all the Flash folders.
Run an elevated command prompt "cmd" (as administrator)
Navigate to each noted flash folder and "takeown" every file in each folder syntax for this is "takeown /f filename.ext" from within the directory. (You can get them all at once by doing "star<dot>star" - Tom's will not let me type in an actual star for some reason). You should get a message success for each file.
You will not be able to delete from cmd (I think because you have not changed the permissions yet).
Exit the cmd prompt.
Go back to the folder in file explorer and you should be able to change permissions (right click on the file name) for each file by security tab in properties - you have to click on Users and edit then again on Users and "edit" to be able to manually set the users permission to full. I am sure you can also set this at the folder level in advanced settings and force inheritance down the file structure but I just did it file by file to savor the victory one deletion at a time.
Go back to the file you just changed and you should be able to delete it.
I had the same issue a few years back. I posted an article and code that automates the unlocking process. It wasn't my work, but I added to it. It's for Win10 and the comments I made are about the old Edge browser. (I need to get back and edit it a bit for the latest info). The article I wrote is for my own info really as each time I visit a new machine to fix for friends etc I need the batch file.
It's helped a few people. If you don't want to copy & paste the code I have a link to the download, but you'll need to right click and save because clicking it in most browsers that are at all serious about security in their settings will block .bat files.