
As such I'll explain how to find out which file or folder is in use using an alternative (and better) method, using Process Explorer.

In cases like this you can use third party programs such as 'unlocker' to unlock the file or folder in use, but based on my experience, it doesn't always work. Oftentimes this can happen - especially over a network share - because the file or folder's thumbnail is being reconstructed usually waiting a few seconds to 'retry' resolves this issue, but not always. The reason why you receive the 'File in use' error (or 'Folder in use' error) is exactly that - the file or folder is in use by some other program, however, Windows isn't saying specifically which program has the file or folder in use (sometimes it does). Can you please tell me why this keeps happening and what I can do to delete the file / folder? "

I click the 'Try again' button multiple times but that rarely ever works. Every once in a while, when I try and delete a folder on my network share, Windows tells me that 'This action can't be completed because the folder or file in it is open in another program'.
