Extract the contents of the ModExporter archive into the OpenMW 0.45 root directory. Then run "start modexporter.bat" file found in the root directory of OpenMW, When you run it for the first time, you'll see the message "Creating "settings.bat file..." When you see this message "Press any key to continue..." then immediately close the window by pressing the "X" in the upper right corner.
Now back to the root directory of OpenMW you'll find "settings.bat" this file was generated in the previous section, right-click and select Edit, modify the following lines to point to PYTHONEXE, GIMPEXE and BLENDEREXE
Python 2.6.6 ("C:\Python26\python.exe")
GIMP 2.8.22 ("C:\GIMP28\bin\gimp-console-2.8.exe")
Blender 2.49b ("C:\Blender249b\blender.exe")
TIP: If you have atleast 10GB of disk space on your C: drive you can leave the MODEXPORTER_OUTPUTROOT line alone, This will place the Resources generated by ModExporter in "C:\Oblivion.output".
If you would like to use another hard drive, then you can change the drive letter from "C:" to something else like "D:". The "Oblivion.output" will automatically be added on and is hardcoded into the scripts, You can not change it.
Now open the Morroblivion.ini file located in your OpenMW root directory. Change the Morrowind line to point to your installation folder for Morrowind, make sure you put "\" at the end of the folder name.
TIP: The Oblivion line is actually the destination folder for output files and not the actual game folder. This must be the drive letter you chose in the "settings.bat" file plus the string "\Oblivion.output\" an example: "C:\Oblivion.output\" or "D:\Oblivion.output\". If you try to name it something else then you will break the Mesh processing stage.
Now create the destination folder that you specified in the above step: "C:\Oblivion.output\" then within this folder, create another named "Data". If these folders already exist, then make sure they are completely empty.
I published the updated version, it's mainly cleaned up, huge thanks to ponyrider0 for all the work on ModExporter and this Tutorial.
Tamriel Data is not out yet, within the next 24 hours it should be.