So I've used a few different tools, like procexp and openfiles. I have noticed however that when running an installer it is able to create a list of in-use files that it is going to overwrite. (Installers will often prompt with this list and give an option to close running instances of previous versions of the software).
The thing is, the installer seems able to do this very quickly, while procexp and openfiles seem quite slow (can take many minutes to run).
What magic is the installer using? Is there a tool available that uses the same magic to quickly find/list open files?