Texconv

Texconv is a command line tool from Microsoft to convert textures to different formats. It is included in the DynDOLOD Standalone and the xEdit/xLODGen download archives.

Texconv uses the GPU via DirectX to speed up processing for certain formats. If there are multiple graphics cards in a system, make sure the best available dedicated graphics card is set as the default.

DynDOLOD includes a customized version of Texconv to convert different texture formats.

It requires a recent version of Microsoft Visual C++ Redistributable packages for Visual Studio 2015, 2017, 2019 and 2022 to be installed.

In case the Redistributable is missing or outdated, typical error codes are C0000135 or VRUNTIME140.DLL/MSVCP140.DLL or similar is missing.

Ensure that Windows User Access Control (UAC), antivir or other third party programs do not prevent execution or read/write access.

Do not replace Texconv with other versions.

Code
Explanation
C0000005

Install, update or repair Microsoft Visual C++ Redistributable packages for Visual Studio 2015, 2017, 2019 and 2022.
Make sure the OS, UAC, anti-vir or some other 3rd party crapware is not interfering.
Install the latest graphics driver only without any of the crapware.
Check the Windows Event log for hints.
See this thread on the official DynDOLOD support forum.

C0000135
Install, update or repair Microsoft Visual C++ Redistributable packages for Visual Studio 2015, 2017, 2019 and 2022.
80004005
The texture is not a valid file format or corrupted and needs to be converted or replaced. Look up the texture path in MOs right window Data tab to find out which mod supplies it. Reinstall the textures from the mod, DynDOLOD Resources or TexGen output, whichever it is. If the mentioned texture is part of the DynDOLOD output, delete the entire output from former session before trying again.
80070003
There is a problem with the mentioned path(s)/filename(s).
Could be a problem with special characters, too long path etc. or the OS, UAC, antivir etc. denying access
80070005
The OS, UAC, antivir etc. denied access.
8007000E
Texconv ran out of memory. Let the OS handle virtual memory settings. Check FAQ answers for High memory usage.
80070020
The file can not be read or written to. Another process or thread is blocking access.
80070026
The texture is corrupted and needs to be replaced. Look up the texture path in MOs right window Data tab to find out which mod supplies it. Reinstall the textures from the mod, DynDOLOD Resources or TexGen output, whichever it is.
80070057
If this happens on Linux, use an uncompressed texture format and compress textures afterwards with a tool that works in that environment ...
80070070
There is not enough space left on the disk to which Texconv is trying to writing to.
800704C8
The file is blocked by another process.
887A0005
There is a problem with Texconv using the graphics card. Make sure the first graphics card in the system has proper DirectX support. Check the Windows event log for related messages. Update/repair graphics card driver. Test if the official release version of Texconv works by concerting a texture on the command prompt. Using the official version instead of the customized version included in the download archive of DynDOLOD will typically not work, so this is just a test to verify more easily that the problem is with the OS, driver, setup etc.