Problems with Lightroom and Nikon D780 NEF files

Not sure what you expect to accomplish by installing Lightroom 3.2.1. As far as the problem you are faced with, the two programs really aren't connected. And judging from other things you have done, I question the wisdom of playing around with your Registry. Honestly, I don't know what you have done with your computer, and I don't know how to help you. I think your best bet is to contact Adobe Customer Care. In the meantime, good luck with whatever you do.

I didn't read that entire link, however "I think" it was only referring about moving the catalog to a different location. I'm not familiar with changing the installation path for Lightroom. I did find this short discussion that you might consider:

https://community.adobe.com/t5/lightroom-classic/need-to-create-a-custom-install-path-for-lr-cc-classic/td-p/9496550?page=1 

You might have to go online with Adobe chat to ask them unless someone else here has better installation skills. Sorry, I just don't know how to instruct you to change that installation path.

Click on the little "balloon" in the lower right-hand corner to initiate a chat session with Adobe:

Adobe Customer Care 

See the link below for should help. If that is not exactly what you wish to do then a simple search on Yahoo or Google will provide dozens of alternatives. I also believe when you are actually doing an install there ought to be an option there.

https://lightroomkillertips.com/moving-classic-catalog-different-drive/ 

P.S. Having another read of your post I think you have to treat this as moving to a new computer. Adobe Creative Cloud may consider that as an additional installation. The thing you will need to keep all your secondary Lightroom file connected with the new installation.

I believe, at least I understand, that you are using Windows 10. Unless you intentionally changed the installation path, this is where Lightroom Classic is installed by default:

If you changed that for some reason, and it is being installed on drive F then I wouldn't worry about it. What makes you believe the installation process is doing that?

The reason you want to compare the list of supported cameras is because Lightroom supports the same cameras as the Camera Raw that it states in the "About" screen. And since you probably have Photoshop installed, you want to ensure that you have the two programs coordinated.

Not that this really matters, but just as a point of interest. When working with Lightroom Classic or even Lightroom (for the cloud), you aren't working with Camera Raw (the plug-in). When it identifies Camera Raw like it does in the "about" screen, it is identifying  which version of Camera Raw for Photoshop your particular version of Lightroom is compatible with. But Lightroom itself has that technology integrated in the program. The only time Camera Raw is updated is when the plug-in itself gets updated. A Lightroom update doesn't necessarily update Camera Raw. Like I said, nothing critical here, it's more of a for your information thing.

In my opinion, you would do well to uninstall that older version of Lightroom. It's confusing you and isn't doing you any good. But that is up to you.

A new piece of information, at least new to me. It appears that you have got two different versions of Lightroom installed on your computer. I don't know how that has happened. Apparently the desktop icon is pointing to the wrong version. I would go to the folder in the Programs folder and find the executable file for Lightroom Classic and create a shortcut and copy that shortcut to the desktop. When you start Lightroom using the icon (The one that won't show your D780 files), when you check the "About" information in the Help menu, what version does it indicate you are using?

This thread has gone inactive. I'm going to make one more comment and then I'm going to completely ignore it. I have been trying to provide assistance. I don't have the Nikon D780. However, I downloaded a series of sample images from a website (all NEF files). I have edited them, closed Lightroom, revisited them the next day and the next day, moved the images from an internal hard drive to an external hard drive, and have always been able to have access to the images to do whatever I wanted to do with them. 

I have been watching to see if you have been able to resolve your issue or have identified where the problem is. Just curious, but not trying to be obnoxious or anything like that. Just wondering what has happened. Your problem has had me puzzled.

So where is the catalog located? Do you have more than one hard drive? Are you using external hard drives in addition to your computer hard drive? Are you using smart previews?

For your information I'm using Lightroom Classic 9.2.1, Windows 10 Home Premium. I have Lightroom Classic installed on my main (C) hard drive, which is a SSD hard drive. The catalog is installed in the default location Pictures\Lightroom folder. My pictures are distributed across two other internal hard drives. I have a few images on the SSD, but at the present time very few of them are linked to Lightroom.

This morning I opened Lightroom, which I closed on the two NEF files from the D780 that I downloaded from the Internet. I stored those in a folder in my Pictures folder on the SSD. As I expected, Lightroom opened and found the images without a problem. I was able to use all of the tools in the Develop module. So I really don't understand what is happening on your computer. There is no logical reason that I can see that you should have to go through a setup.exe every time you want to work on NEF files from the D780.

I'm not sure what you are referring to when you mention filter files and their location. Maybe I'm not up on filters. But you really shouldn't have to be messing around with the location of the catalog. That should remain constant. Unless you have done something different it should be in a Lightroom folder within the Pictures folder. That is the default location. Of course, the catalog can be in any folder of your choosing IF you have moved it. You say your catalog is growing fast (around 1 MB)? That's not very big at all. That seems a catalog with nothing in it. There is a tool to optimize the catalog. On a Mac it's under the Lightroom menu, on a Windows computer it's under the File menu. And if you're backing up your catalog on a regular basis there is an option on the back Dialogue to test the integrity of the catalog during the backup process. Are you doing that?

I never had to reset the location of my catalog. That information seems to be a constant. I have never had to run any kind of a setup.exe other than to install an update to Lightroom Classic. I haven't even seen the name of that file for quite some time now as those updates seem to be handled from the creative cloud manager. It notifies me when there's an update, does the updates, and I move on. Something just seems to be out of whack with what you are doing, it seems.

What is this setup program that you refer to? Do you mean that you have to run this setup every time before you can work on these D780 images? What settings are you having to adjust in the setup program in order to make the editing possible? I have two sample NEF files from the D780 that I downloaded from the Internet. I'm using Lightroom Classic 9.2.1 on Windows 10 Home Premium. They load and edit without any issue. I can quit the program, return to the program without a problem. I will report tomorrow, but I don't expect any issue getting back to the images again.