the action can't be completed because the folder or a file in it is open in another program

Useless advice.  It is not enabled.  Windows 10 sucks at this.  It hangs on to everything.  Refuses to grant Ownership to the f'g OWNER!  It causes me hours per week that never happened on 7 Pro.  Total garbage.

In fact, since I dual boot, sometimes I have to go back to W7 and get the job done.  Unfortunately many times I can't if files in question are denied access from the other user account.  W10 needs a major fix on access and permissions.  I want a faithful servant not an authoritarian despot.

RCL

This and every other related response I have seen is a WORKAROUND, not a SOLUTION. We can all feel good about coming up with these ways to overcome this BUG in Windows H8. But I haven't seen a FIX to the operating system that ELIMINATES PERMANENTLY this UNDESIRABLE FEATURE.

I've encountered this before, as many have, and this time I could not remember how I fixed it prior.

Finally, an option came to me this afternoon that worked for two LOCKED mkv files and I figured I'd share the fix for others to use.

My fix works for MKV files because of the tool I used, is very likely there are equivalents to free up other types of media files.

That's the catch, as these LOCKED files are ALWAYS a media file of some type, and I had two of six all in order in a directory. All different episodes of same source, named identical but for episode number. The two locked ones, couldn't do nothing but copy them and that just created two more identical problems.

Started looking at the file properties and the two bad ones would NOT display a time length or resolution in the lower Explorer Preview Window (Win 7 Home Premium SP1 64bit), while the four good ones would display that data.

THAT is the 'tell' to see which ones are locked up, as this is some sort of thumbnail type issue, but disabling thumbnails didn't help me.

Program called 'MKVMerge GUI subtitle fixer' and I can demux and remux an mkv file, adding or removing language and/or subtitle files. For the two trouble files, I simply dragged bad file #1 to it, and ran a simple de and re mux, adding nothing and steering a newly named file in a sub directory.

3 minutes later, Voila! Sweet!. Did it for the other file, then on to deleting those little buggers....

Should add each file was like a tiny 15k bigger and they both now displayed the missing time and resolution data that was missing. Files were IDENTICAL in quality and nothing changed, just separated the audio and video and put them back together, properly.

To delete, you need to restart your PC and make sure NO Windows Explorer opens on the restart (Close them before you restart), once Windows Explorer starts, you are already locked out for the duration.

Immediately after the restart is complete, Open a command prompt and navigate to the folder(s) of the offending file(s), then you can delete them using good old DOS commands, which there are MS help files on. You try that without restarting and you'll get that same irritating message in DOS form, word for frigging word, arrgghh!!

Do NOT open Windows Explorer until you are done, or wanna check and see how it worked, but you'll have to restart again to recreate the 'magic'.

Is a long way over the river and through the woods, but am writing this from Grandma's house, I made it.

Good Luck Everyone - Be Nice to Someone that isn't expecting it, you can change the world.

8-)

In windows 8 in the view toolbar Press the Preview pane to turn preview pane off. 

This opens a preview of the file which locks it from being deleted.