The solution posted by Viper Arrow on BSF -
How to fix the Error "Failed to load snowflake: Meshes\BM_Snow01.nif"
To fix this you need to install the games manually
First to solve the Failed to load snowflake: Meshes\BM_Snow01.nif. Insert the Bloodmoon expansion CD into your CD/DVD drive next navigate to
C:\Program Files\Bethesda Softworks\Morrowind\Data Files\Meshes and leave that window open. Next (make sure the Bloodmoon CD is in your drive) go to Computer and right click (D:/) Bloodmoon and click explore then go to the Datafiles folder on the CD. You should notice other sub folders called
First go to Meshes on the CD and copy EVERYTHING into the Meshes folder that you already have open (C:\Program Files\Bethesda Softworks\Morrowind\Data Files\Meshes), by clicking and dragging. This should solve the snowflake error.
If you start the game with this done you should notice that instead of the snowflake error you should get a new one. This shows that it’s working and that the game is using the textures that you supplied. So now do the same with every folder in the data files folder on that CD BookArt into the BookArt folder Textures in the Textures folder etc. etc. With that all done try run your game and it should work, finally!
But after a while you should notice more errors. To test this go to the trader in Seyda Neen and an error will appear in the loading of the interior about a missing texture called Netch leather cuirass. This is a texture that was supplied with the Tribunal CD, so more manual copying. Insert the Tribunal CD into your drive, right click explore, go to the data files folder and do the same that you did with the Bloodmoon CD but the only problem is that this time you need to go to the separate sub folders and place them into the separate sub folders on C:\Program Files\Bethesda Softworks\Morrowind\Data Files meshes textures etc. because Bloodmoon already created them. You need to go this because if you just select everything in the Tribunal meshes folder and click and drag into the data files folder on you C:/ drive it will overwrite the existing Bloodmoon files this should then fix all if not most of Vista's missing texture problems.