I think I may have to give up! . . . Am I dumb or what?
1 - No, you cannot give up. We will not allow it. If you did that, Oion and I would be banished and left forever to float in cyberspace as mere bits and bytes -- remnants of our former selves. You wouldn't want that on your conscience, would you?
2 - No, you are not dumb. You found this place, registered and managed to post your problem in a coherent manner. That, alone, puts you on the far right side of the "Bell Curve." A lot of people cannot do the first; fewer can do the second, and a very large number cannot manage the last. (Are we done with that subject? I really, really, hate having to repeat myself -- but I will, if necessary.)
Ok, let's start over. I am flailing a bit here, because I don't know which reader apps you are using and am probably not familiar with them, anyhow. So, I will make some simplifying assumptions in this process.
1 - This is important: Take a deeeep breath. Exhale. Finished? Good; now we can move on.
2 - You have downloaded or transferred some number of books to some number of locations. If they are epub files, most of them will have recognizable names. Some of them came (presumably) from the Sony reader. I don't know their file naming conventions, so they may not be recognizable.
3 - It doesn't matter where you put the book files if your reader app has navigation ability (e.g., Freda). Some apps are preset to open to their own default folder (e.g., Kindle)
4 - File Explorer is your friend. It will work better with a mouse for this sort of thing, but that is not a firm requirement.
5 - I'm going to use Freda as my example, because I know how it works. There will be useful parallels with the other apps
6 - Open Freda, note the name of the folder to which it opens. Identify any unreadable files in that folder.
7 - Open File Explorer and navigate to that folder. Delete the unreadable files.
8 - Hopefully, that left you with at least one readable file. If so, open it and try reading it. If you can read at least one book file, then we have cracked the code.
9 - If not, find one of your downloaded, non-DRM files and move it to that folder. Again, if you can read just one, we have solved most of the problem.
10 - Identify the one to three reader apps you prefer at this point, and lets work on them (I used Freda because the guy who developed it used to post here -- as good a reason as any.)
11 - Tell us what those apps are, so we can be looking at the same thing you are. I will install them on my RT for ease of communication.
12 - Don't worry about cleaning up the other trash right now. We can do that when we have you satisfactorily reading.
13 - I'm in the Eastern time zone, so I'm gonna throw my dogs out and go to bed. I will check on you in the morning.
14 - Meanwhile, you cannot quit and you are not dumb! Got that? Good.