In message , VanguardLH
writes:
J. P. Gilliver (John) wrote:

I go to a folder with .webm and .mp4 files in it. The .webm ones have a
traffic cone (VLC), the .mp4 ones a waveform (WinAmp). I want them all
to open in VLC, so I right-click on one of the .mp4 ones, select "Open
with", ignore the VLC option and select "Choose default program", and
select VLC there.

The file opens in VLC, and when I subsequently look at the folder, all
are traffic cones and open in VLC.

But at _some_ time subsequently, the .mp4 files are back with WinAmp. I

***
don't _think_ I've got WinAmp's "protect my associations" turned on
***

(even if I have, why does it allow the change temporarily?).

Some apps are very rude. When you load them, they re-associate
filetypes to themselves. It's been awhile since I hit a program like
that but it's been way too long to remember what was the program (I
vaguely recall it was RealPlayer). All its users complained about it
*stealing* the file associations. Eventually the program stopped
stealing the file association just because the user loaded it.

RealPlayer _was_ a terror at doing it, at one time.

https://www.google.com/search?q=wina...%20association

That shows users complaining about WinAmp rudely and covertly stealing
file associations to assign to itself. While some posts are old (circa
2000), WinAmp is also old (last updated back in 2013). Perhaps there is
a user configurable setting regarding WinAmp's behavior to *not* have it
steal file associations to itself. That is, maybe there is an option to
associate certain filetypes to itself when loaded but you can disable
that "feature".
See above: I didn't think I had it on. I've just checked, and in Options
| Preferences (I have version 5.61), there's a box labelled "Enable
Winamp agent", below which is the explanation "Winamp agent can maintain
your Winamp file associations and show an icon in the system tray.

Disabling this feature may result in other applications launching when
you open media files from Windows Explorer."

I do _not_ have that box ticked.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

After all is said and done, usually more is said.