Okay, it took me a while to get to try this, and there was a lot to try. Thanks again for your help.

Removing the Plugin Path line from operaprefs.ini had no effect (and there is no handlers.ini on the entire machine).

I fiddled with the .DLL versions inside plugin-ignore.ini and on the hard drive; Opera is not blocking all of them indiscriminately.

Everything is 32-bit: the CPU, the OS, and Opera itself.

I fiddled with the .DLL versions inside the system folder where the newer Flash DLL is, it will only pick up the newer .DLL. If I tell it to ignore the newer .DLL, then it uses nothing.

I tried renaming the operaprefs.ini as "handlers.ini"; no luck there either.

The only thing that comes close: I renamed the v10 .DLL to the one that Opera seems to seek out, and that tricks Opera into using the v10 .DLL. The only problem with that approach is that Firefox is trying to use that same .DLL (registry?). Again, I was hoping to get one browser to use one Flash version and the other browser to use a different Flash version, since some Flash versions play videos better than others, and vice versa.

I really appreciate your help, but I am thinking of throwing in the towel and trying a different browser. I'm usually very persistent, but I know I am fighting a losing battle as I try to keep this single-core 3 GHz machine going for my folks. You would think 3 billion operations per second would be enough to watch some web video, but not if Adobe's bloated software has anything to do with it, apparently (BTW, I am a programmer). I have been an Opera fan from so long ago, that I actually PAID ($40?) to have its built-in ads removed (version 4 or 5?), so I was interested in hanging on but there's only so much time an adult can dedicate to "the trivial". Thank you all for your posts, especially @burnout426.

Thanks again to all.

@burnout426, the plugin-ignore.ini procedure worked; it keeps Opera from using Flash DLL v14. However (and this is my original question), I cannot edit the path where Opera points to a different Flash DLL - it is not editable within Opera ("Alt + p -> advanced -> downloads"); in fact, that text box is now blank since I told it to ignore v14.

Version 10 of Flash DLL sits on the hard drive in:

C:\Program Files\Opera\program\plugins

and Opera's config/User Prefs/Plugin Paths points to that directory, but the "Use Plugin" pull down list inside Opera is still empty after a restart.

Holy cow! I bow in honor of your extensive Opera knowledge. Thank you for your time and your detailed post.

Cutting to the chase, my registry has those branches but they are:

HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashPlayerPlugin
HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins@adobe.com/FlashPlayer

There is a

HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\

too; but it has no such plugin info., etc. I don't know whether that matters.

For starters, the Windows' registry search function failed me; "NPSWF32_14_0_0_125.dll" DOES exist in the above registry branches, but a search does not find them.

I guess my next point is summed up like this: I want FireFox to always use Flash plugin NPSWF32_14... I want Opera to always use an older Flash version. Is this possible then, if both browsers point to the same spot in the registry? Further, if the registry points to the Flash DLLs, then is Opera's opera:config plugin path irrelevant for Flash?

Thank you very much.

The same version of Opera is installed on both?

Yes; 12 is on both machines.

Opera probably gets it from the register.

I searched the Windows registry: there is no instance of the Flash plug-in .DLL filename.

Usually flash can be found under Windows dir and/or %appdata%.

I can find the Flash DLLs in various places on the hard drive, but I can't find where/how to edit which plug-in Opera uses.

Where does About Opera say your profile folder is?

"Opera:about" in the URL bar returns: "Opera Directory: C:\Program Files\Opera\profile".

Are both computers using version 12?

Yes; 12 is on both machines.

In 12, you can go to Preferences > Advanced > Downloads and edit things there.

It won't let me edit there; it only shows the path/filename of the plug-in.

The whole issue is quite odd. But thank you all again for your help. I will fiddle with it some more and post here if I find a solution. However, I am also going to install the Vivaldi browser and see whether that gets me what I want.

Okay... My personal machine has a handlers.ini. The target machine does not - I scanned the entire hard drive and no files/folders are hidden on the machine.

I also scanned its Windows XP registry and found no instance of the Flash .DLL file that Opera claims it's using (under "opera:plugins").

If a machine does not have a handlers.ini, where is the path for the Flash driver kept so that Opera can read it when executed?

So if there is no handlers.ini anywhere on the machine, is the hard drive/Opera installation corrupt? I mean, MUST there be a handlers.ini somewhere? (An Agent Ransack search comes up empty.)

Well then, the question remains: Where is this information kept (if not in "handlers.ini" in "C:\Documents and Settings")? A reinstall changed nothing. Thanks to all.

Update:
I was confused: The pertinent data is in a file named "handlers.ini" - I might be able to edit things there. This file (and for that matter the entire Opera folder) is missing from "C:\Documents and Settings" for some reason on the troubled/target machine, whereas it is present on my machine. I will try reinstalling Opera and go from there.

Thank you for your help.

I scanned my hard drive for "handlers.ini", there was no such file.

I tried putting the npswf32.dll in Opera's plugins folder, but Opera does not show it when looking at its settings after restarting Opera.

I put "opera:plugins" in my version (12) which only shows the plugins, but does not allow editing other than enable/disable.

I appreciate your attempts though.

In Opera 12 for the PC, you can see the plug-in used for .SWF files by clicking Tools/Preferences/Downloads/{find .SWF}/Edit...

The path & file ("npswf32.dll") pointed to by Opera exists on my hard drive, but I cannot change that filename or path within Opera. Does anyone know whether I could manually edit a file where Opera stores this information? I'd like to be able to change Flash plug-ins with a quick restart of Opera versus an entire re-install of Flash.