Issues with replacing System32's authui.dll, needing help to fix it.

I apologize in advance if I am posting this problem in the wrong area, though I am in a bit of a panic and require assistance very badly with some involving System32 .dll's. To explain how I got into this issue, I was trying to follow a tutorial on how to remove the profile image from the logon screen of Windows 7 (with all working well until just now) and recently hit a large bump in the road. (in case my explanation is not exactly understandable since I might say something jumbled or confusing, apologies on that, here is the tutorial I was following. windows 7 - How to remove the User picture from Login and Lock screen? - Super User ) On the tutorial it gave two options one for people to edit the authui.dll themselves to receive what they wanted, and download a pre-edited authui.dll for those not confident enough to edit the registry. I of course chose the latter. All was going well, I changed the ownership of the original authui.dll and make a copy of it onto my desktop just in case, then changed the original to a .bak like the tutorial said, his is where the issue arose. I dragged and dropped the new Authui.dll into System32, it flashed saying I needed admin confirmation to do so, hit the button with the blue and yellow shield, and after the final flash nothing happened. I cannot put the replacement into System32, so now I have a copy on my desktop, a replacement ready to drag, and an authui.dll.bak inside System32 WITHOUT any actual authui.dll. I'm no mastermind of computers, but I think I know enough here to believe that if my computer were to restart right now, I am essentially royally screwed. This is why I need assistance, I need to know how I can somehow put the new authui.dll into System32, or at least know how to turn the authui.dll.bak into a .dll again, because I can't even do that, it says "Can't access control editor. A device attached to this system is not functioning" so I need to know if I can fix this or if I have to reinstall Windows at this point. I am hoping someone can help me out here somehow. (I apologize if I typed more than needed, I am just really desperate for an answer right now)

I have exactly the same problem, I think microsoft updated this a while ago. I had already removed my profile pic on the logon screen with the exact same method. Today I tried it several times and I ended up with restoring my windows via the windows cd. Seems like editing the authui.dll is no option anymore. It is still working on my Laptop though, very strange.
I also tried to move files by stopping the explorer.exe via taskmanager, and coorinate with winrar.exe. didn't help either. Also register and unrigister the .dll via cmd did not help.