I mostly use notepad++ for every document file possible on my 2 machine. But sometimes something going wrong with it.
When I open any document with notepad++ and I close the tab of this document, Notepad++ sets this file "in use" and thats why I can not delete the file (but I don't close Notepad++).
Normally this should not happened. Also I should say that this is not happening every time. But I use 2 machines with notepad++, and this is happenening 2-3 times in a day.