depends.exe for Windows

Depends.exe is a free utility that can be run on a Windows executable or dll and builds a tree of all the modules the paths where they can be found, base address, version numbers, machine type. It also shows what functions are exported by the module and which of those functions are being called.

Why or when do you want to run it?

If you need to troubleshoot errors related to loading and executing any module on Windows.
It detects missing modules dlls, circular dependency errors and other errors.