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

What are the exclamation marks for?  Looking to recruit others to some restart fetish you have?  We know this.  We know we can restart.  Look, if someone gets constantly constipated after eating normal food, there's something wrong and the body needs attention.  "Hey, just get an enema!"  That's how stupid your response is.  There is no answer but a correct one.  Every time people write kindly an inappropriate workaround response to such an inexcusable problem, Microsoft gets a pass.  "Hey, see those people will deal with this, we don't have to do anything".   No single answer in this thread, or other threads with issues as ridiculous as this problem is, should be at all apologetic.  It's great to help pitiful customers find a temporary solution, but those temporary solutions should at all times be accompanied with seething contempt for a company who has amassed so much money from us that every feature in any OS they've launched since XP should be bomb proof from day 1. 

No more of this "hey, restart your computer, it's a happy day!" BS  Do you live in some kind of group home for crying out loud?

Of course my setting for "Launch folder windows in a separate process" was already disabled.  But get this, I enabled it, then disabled it and now it works.

Ok, this issue just started two days ago for some unknown reason.  No one really messes with the computers other than me and I haven't touched this laptop in a while. In fact, the last time was when the paralegal mistakenly hit "yes" on the Windows 8.1 update annoying popup.  Before it completed she told me so I successfully DID NOT accept the EULA and it rolled back the changes.  That only stole an hour from our day.

So evidently now the hidden, cached image from the preview pane prevents deletion of a file.  When I switched the view option now the preview pane says No preview available. 

C'mon Microsoft, stop messing around!

I actually had to disable the "show preview handlers in a preview pane" in the Windows Explorer, options, view Tab.  I was then able to easily delete all my sticky files not deleting because I do have my preview pane setting to on.

Interesting... I'll definitely give that a try and report back. 

If others don't aren't clear about this:

In Explorer go to View Tab

Select Options button on right

Select the View tab on the Folder Options window

In the Advance Settings window deselect Show preview handlers in preview pane

With respect, everybody on this forum is upset. But you and MAFury could be said to "clog the forum" with fix-the-forum-users solutions. If Microsoft was going to do something about this here, they've had since March 21, 2013, when the thread started, to intervene. I don't think that keeping the forum nice and unclogged for them would have upped their motivation to take action in anyway, here or anywhere else.  Meantime, people do the best they can as they wait for Godot. Just curious, but why do you think Ma Fury is a "him".... You looked under his kilt? I’m sure I speak for most “end-users” here in sending commiserations to your "end-users". Best.