Thank you all for your help and support. The problem is solved.
The problem was solved very simply to such an extent that it made me laugh))).
I took my purchased certificate from the 12th version and inserted the registration data in the Directory Opus 8.2.2.5 ANSI and the program was activated!!!
Here is a screenshot confirming this:
That's what Jon was talking about, although I'm surprised it works as far back as version 8. Maybe 6 was the only Opus version for Windows that didn't use certificates, but we're talking about almost 20 years ago so it's hard to remember.
Great news! That's why opus is an excellent piece of software 
I know I'm necroing this thread, but I thought it might be preferable to keep the conversations about this here, and to just demonstrate that there are still valid reasons to use software on ancient operating systems.
I have a couple of (yes, ancient) Windows 2000 virtual machines (I converted them from physical to virtual in the last 10 years or so) that I need to maintain just to keep being able to refer to some proprietary program's database of information I kept, and would not be cheap or easy to get all the data out in a format that made sense. All efforts are in order to keep everything as-is so that there's less chance of anything going wrong, losing data, or losing the capability of accessing that data. The proprietary software I have on them is complex to set up from scratch, and at this point I don't even know if these old versions of the software would work on a much newer Windows installation.
I've been trying to slowly optimize these VMs, which is itself a painfully slow process, in order to get them to work as well as possible. I've run into a snag and have need to use DOpus, likely via portable USB connected to these VMWare VMs, which I would create through an intermediary old Windows installation in a VM, to verify and potentially solve some remaining quirks I have - especially with one of the VMs.
Is v8.2.2.5 the last version that worked with Windows 2000?
I can only find as old as v9 elsewhere so far, and I hate to get into increasingly questionable source websites for this purpose since the data on these VMs is critical, although I have plenty of backups.
Found 8.2.2.5 after all, on a reputable enough and relied-on website.
I am sad that I can only go back as far as v10 with officially supplied installers. I'm glad I'll at least be able to use my v12 license with whatever old version I can.
Edit: Looks like it'll take 2.5-3 hours to download this ISO that has the installer for 8.2.2.5 on it, so yeah...a quicker download method would be nice. 
Have you considered administering them over the network?
Thanks, Jon.
These Windows 2000s installations in VMs are so slow, I feel that attempting things indirectly would be an added headache that would likely just add to the list of things needing solved. 
They are even so fragile that I can't perform power on or off options on both VMs at the same time. I need to wait until one is fully done and auto-logged in before powering on the other.
I'm also avoiding installing anything on these VMs that I don't have to, hence why I'll use DOpus portable on them.
I've got them on the most recent VMWare virtual hardware revision (and VMWare Tools) that supported Windows 2000. I had briefly tried upgrading the VMs to the latest virtual hardware, which did wonders for their boot time (maybe 10-15 minutes insted of an hour or more each), but broke all actual ability to use the VMs.
So I restored them to my backups, which I had already spent many hours optimizing from their original configuration, and I'm doing everything I can until there's nothing else I can think of, and then I'll do yet another backup and attempt a much more slight virtual hardware upgrade just to see what happens, even though I know newer VMs didn't support 2000, so I don't expect much from that angle.
Edit: Can you tell me if v8.2.2.5 was the last version that supported Windows 2000?
I can't remember 16 years ago but searching the New Releases - Directory Opus Resource Centre area for "2000" shows Opus 9 still worked on Windows 2000, at least at release, and I can't find anything saying we dropped it before Opus 10.
Oh, thank you! I should've thought to search that way - sometimes I do, but when I found this thread, I got tunnel-vision.
I've now PM'd another user who offered to provide a link to v9.5.7.0 just a few months ago in another thread here, to see if they can provide me with it.
Cheers and good to see you around.
9.5.6.0 is the latest version of 9 I have an installer for, so that's newer than mine. 
Ah! The user had said in the other thread that they had 9.5.6.0 64-bit, but 9.5.7.0 32-bit (which is what I need). Is the installer you're referring to 64-bit? Was there ever a silently released update? I don't find any other reference to 9.5.7.0 except that other thread, where they, too, appear a little perplexed at their own lack of having the 9.5.7.0 64-bit version.
It's so long ago I can't remember.
Back in the days how DOpus was shipping was so stylish. 
(No, not mine, i think i started with version 8)
I had it reversed in that post.
I have 32-bit 9.5.6.0 and 64-bit 9.5.7.0 .
I don't know what happened to 32-bit 9.5.7.0 .
As you don't have it either, perhaps 9.5.7.0 was a 64-bit bug fix ???
Sorry for the confusion.
I guess there were a couple of 5¼" floppys and a manual inside.
I had 3.5" drives on my Amigas, although evidently 5.25" drives for those did exist, according to a quick search. I remember I was so happy when DOpus 6 was being developed for Windows XP.
from fred fish cd
there was never a 9.5.7.0
if there was, I would have that.
not even in english
our installer always had the german/english language
I also had the 4 box (go searching)
found 5 directly
I still carry it today
The mystery is now solved.
It was filed in the incorrect folder and renamed DOpusInstall_64_9.5.7.0.exe .
But it is different than the other Directory Opus 9 files in that folder. It has a different icon and a larger file size.
And in my Directory Opus 10 folder, 10.5.7.0 64-bit is missing .
Notice that screenshot shows "File Version: 10.5.7.0", hence the confusion. I think the mystery is solved, it's actually 10.5.7.0 (I assume 64-bit). I was wondering about the identical sub-version numbers for the last 9.x and 10.x being the same.
Sadly, this may mean you don't have the last 64-bit 9.x version at all - not that it affects me. Although it appears @Nobmen has it.
