Question: I built a .pyd in Visual Studio 2019 (Community) that provides a wrapper for some functionality that's only present in the LibRaw. The solution compiles successfully without any warnings or errors. The project uses LibRaw, OpenCV and pybind11 as well as Python.h and the corresponding .lib-file. When i try to import the .pyd inside the Python Interpreter i get: C:\Users\Tim.Hilt\source\repos\cr3_converter\Release>dir Datenträger in Laufwerk C: ist Acer Volumeseriennummer: EC36-E45E Verzeichnis von C:\Users\Tim.Hilt\source\repos\cr3_converter\Release 22.01.2020 11:28 <DIR> . 22.01.2020 11:28 <DIR> .. 22.01.2020 11:28 808 cr3_converter.exp 22.01.2020 11:28 3.068.361 cr3_converter.iobj 22.01.2020 11:28 785.552 cr3_converter.ipdb 22.01.2020 11:28 1.908 cr3_converter.lib 22.01.2020 11:28 4.190.208 cr3_converter.pdb 22.01.2020 11:28 953.856 cr3_converter.pyd 31.10.2019 16:22 26.408.085 IMG_0482_raw.CR3 7 Datei(en), 35.408.778 Bytes 2 Verzeichnis(se), 77.160.587.264 Bytes frei C:\Users\Tim.Hilt\source\repos\cr3_converter\Release>python Python 3.8.1 (tags/v3.8.1:1b293b6, Dec 18 2019, 22:39:24) [MSC v.1916 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import cr3_converter Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: DLL load failed while importing cr3_converter: The specified module was not found. >>> import cr3_converter.pyd Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: DLL load failed while importing cr3_converter: The specified module was not found. >>>  The Paths to the needed .dlls (Python and OpenCV in this case; LibRaw was linked fully statically) are set in the system-path. I ran Dependency-Walker, but could not find anything suspicious. Here is the corresponding Dependency Walker image. I also tried out another tool (Dependencies.exe, which is essentially a rewrite of Dependency Walker, but takes into account the API-MS-WIN-CORE-....dlls) and got an error, which looked like this:  When i hover over the missing .dll, i can see a api-ms-win... module could not be found on disk. I have searched and found the module and added its directory-path to the system-path. Now the module isn't highlighted red anymore, but the C:\WINDOWS\SysWOW64\WS2_32.dll (red highlight at top of screenshot) still shows to have missing imports. Could this be an issue? How i've produced the .pyd:  Created empty Visual Studio project (Win32; Python is also the 32-bit-installation) Changed project-settings to .dll-configuration and .pyd-fileextension Added include-paths to the header files for OpenCV, LibRaw and Pybind11 Added paths and input files for the linker for OpenCV, LibRaw and Python3.8 Built the solution (No Errors, No Warnings) Tried to import the resulting .pyd in the python-interpreter  I've seen this question, where the OP had the problem of different Python-.dlls being loaded by the library, but in my case the library referenced by Dependency Walker is the same as the one i have in my path-variable.

Answer: I quietly assumed, that Windows searches for .dlls in the same directories as the ones listed in the systems (/users) PATH-variable. However, that is not the case, as ProcMon revealed. For now, i copied the missing .dlls to the folder that contains the .pyd and everything works.