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

Given what everyone else says about disabling thumbs.db etc, I think I figured out what the issue is, for folders anyway, and at least one other thing that could set it off if I'm right.

Windows 7 (and I presume 8 as well) has a nifty feature whereby it shows a preview of folder contents on the icon when set to any of the following view options:  Extra Large, Large, or medium icons, tiles, or content.  It also shows the 'large icons' version in the details pane at the bottom of the window when you click on a folder.  For images, videos, or audio files with album art, it shows a thumbnail of said for the content preview.  There's also some method by which it'll represent subfolders with an image.

For files with preview thumbnails, (IE: Images, videos, or audio files with album art), on the same view settings where folders show a preview of contents, the file will be represented with a thumbnail preview instead of a file icon.  The 'preview pane' will also show an expanded version of the preview thumbnail when the file is clicked on.

It is my belief that what is generally happening for most people, is that in order for these preview options to work, explorer has to briefly load the file in question to retrieve/generate the thumbnail, thus putting said file 'in use'.  It's not real spectacular about unlocking it after it's loaded it, but seems to have some kind of cache so it doesn't have to re-load it if you come back later. (Maybe getting it out of the thumbs.db file?  No idea.)  Because what I've noticed is that closing the window, or changing it to a different view and then going back to the current one (even so much as hitting back and then forward again) will usually unlock it.

I have also found, however, that changing the view type to one of the 'small icons' types (Small Icons, Details, or List) as well as disabling the details AND preview panes seems to prevent it getting locked in the first place, presumably because that disables all the different 'content previews'.

Wow, looked through all these suggestions... none are helpful.  I agree with the majority here, FIX IT!  I never have this problem on a Mac. Please, if someone finds a real solution, I'm ready to hear it!!

Wow, looked through all these suggestions... none are helpful.  I agree with the majority here, FIX IT!  I never have this problem on a Mac. Please, if someone finds a real solution, I'm ready to hear it!!

I love it.  I detail exactly what's causing the problem AND how to avoid it in the post before this, and you don't even bother to read it :P

As an addendum to what I said earlier, my personal speculation is this only happens the FIRST time windows explorer has to load the thumbnails in question, because it hasn't got them cached in thumbs.db yet.  Trick is, it seems to store them on a folder-by-folder basis, and even then only when the preview actually shows up on screen.

Say it's your music library, you've never really used anything but player software to go through the contents.  You're going through and trying to clean it up.  Any of the following things will then lock the folder:

You're set to an icon size that has previews, and scroll down to where the folder is visible for the first time.

You're set to a small icon size and click on the folder, bringing up the preview in the details pane.

You've already brought up the top level folder preview somehow previously, but not the subfolder.  You then enter the folder, and one of the above happens with the subfolder.  (each folder has its own thumbs.db!)

You've already triggered the subfolder preview previously, but haven't been inside it.  You go into the subfolder, and trigger one of the above with one or more of the files.  Or the latter case, but with the preview pane instead of the details pane.

In short, there are three ways to avoid the issue:

Have previously browsed the folders and triggered their preview thumbnails, so it doesn't have to load the files to get them.

Disable preview thumbnails entirely, which is harder to undo then the last option:

Turn off *all* options that can generate a preview thumbnail:  the details pane, the preview pane, and setting your 'view' size to 'small icons', 'list', or 'details'.  You *must* do all three, or one of the others will trigger the problem again.

I read what you wrote.  And I read your last comment also. 

Maybe I'm just dumb, but what you're saying doesn't help me. 

You are describing my situation exactly... I'm having problems with my music files in Explorer. 

But it still happens when I have my music software (Windows Media Player) closed, and I am in Details view in Windows Explorer. There are no thumbnail views anywhere and it still gives me trouble.