How to know which application is locked a file from deleting and how to solve such issues?

Most of you might have such situations that when you trying to change, move or delete a file/folder Windows denied it , and says it is used by another application.
Windows only suggests closing all applications that may be using the file, but it's not clear what specific applications are meant. Though, often it can be solved by a rebooting, but not always. Is there any effective method of handling locked files and folders without a reboot?

EMCO Unlock IT is a neat free utility that helps you to take control of any file or folder when it is locked by some application or system.For every locked resource, it enables you to see a list of processes that control it.
You can identify respective applications and close them down in a natural way by following all required procedures, such as saving opened files, etc, or you can kill the processes directly from tool. This can be helpful when you remove any viruses or spyware that grabbed control of your files.
EMCO Unlock IT is a very simple to use tool. After installation, slect a file or folder that causing trouble to you (or by just right clicking on the file or folder) and click on ‘Check’ button to see the details. Then click on Kill button to terminate all process.
EMCO Unlock IT works with Windows 7, Vista and XP (32/64bits). Download it at source.