This might have been pointed out before, I'm quite a bit behind in watching the VODs, but I saw Casey looking for XInput-DLLs using dir.
Since I've had so many coworkers not know about this handy little cmdline tool I figured I might point this out in case it isn't widely known: "where" is a Windows cmdline tool that will list the position(s) of that file in the filesystem IF any can be found (e.g. try "where xinput*.*"). It uses the same logic (as far as I can tell) that DLL loading etc. use (current folder, PATH, ...).
It's very fast, but the best part is it also gives you the order of where the system looks for that file if there is more than one, which can be a welcome help if you get stuck in DLL hell.