@rvqx2 :-
So; having got you in the correct location, I'll now answer your question.
I'm assuming you want to put your .mp4 file on the desktop so that you can just click on it, and it will play.....yes? Simple. Open a ROX window where your .mp4 file is. Now; drag the file, and.....drop it on the desktop. You want to play it? Click on it.....and it'll launch in VLC. It's THAT simple in our Pup.
See, this is one thing you need to understand about this particular aspect of Puppy. Unlike Windows - or indeed, most other Linux distros, come to that - where the 'Desktop' is an actual separate location, Puppy's 'desktop' doesn't work the same at all. The Puppy 'desktop' is in fact a creation of two things; panels (provided by the JWM window manager).....and a 'grid' for locating icons/files, etc. This 'grid' is known as the 'pinboard'.....and it's actually an extension of the ROX file-manager.
So; anything you put onto the desktop is automatically a 'link' to that file's 'real' location.....which will be somewhere else ALSO accessible by the ROX file-manager. You cannot copy the file to the 'desktop', because all you will ever do is simply to link it to another location in the filesystem. This is how Puppy's 'desktop' functions, y'see.
When you want to copy a file from one location in ROX to another location, you'd normally open two windows, then drag from one followed by dropping in the other.....at which point a wee window pops-up offering options such as 'Copy', 'Move', 'Link', etc. You click the option, and the 'action' takes place. But the 'desktop' is a special use-case; although it's part of ROX, it doesn't follow quite the same rules as the rest of ROX. Like you never see that wee options window. Because you're NOT in fact copying. All you ever do here is to link.
Puppy's sym-link function is VERY powerful, and extremely versatile. You want to have the file on the desktop, so you can just click on it to play it? Then click on it. It'll open up in VLC, and play.....guaranteed.
Hopefully, this makes sense. (I, too, have quite a soft spot for Tahrpup. It was the first Puppy where everything just worked, OOTB, on all my old hardware of the time around a decade ago. You're in good company with this one.)
Mike.
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(@rockedge :- I only ever use the Desktop folder for one thing, Erik. If I'm setting up a web-page from one of the Chromium 'clones' to open in its own separate window - my way of creating a 'desktop app' - I have to create a .desktop entry into the system. This .desktop entry, as part of its ceation, automatically generates a random alphanumeric string.....the 'desktop app's' ID. And ~/Desktop is where the browser will always send it...
After more than a decade with Puppy, I know for a fact that with JWM/ROX, you won't ever 'see' desktop items in ~/Desktop. Not like you will with Thunar's 'Desktop' directory. Again, it doesn't 'work' quite the same as most people would expect it to.)