So, like many of you, I recently have fallen victim to the NV crash that happens when launched from steam (Immediate crash upon startup at the splash screen. And like many of you, I searched high and low for a fix on this forum. I updated drivers, DX, uninstalled and reinstalled countless times, reset cache, checked integrity, everything and yet I was still coming up with the exact same error. Now, Bethesda, in all their glory tells you to delete your .ini files though in their hastiness they forgot to tell you where they are at and how many. I have found a solution that has so far, allowed me to play the game (past the splash crash) 100% of the time.

inside your Libraries (For those with windows 7 C:\Users\%User%\Documents\My Games\FalloutNV), there's a folder called My Games, inside that is another folder called FalloutNV, inside that are two config files that are NOT deleted when you uninstall and reinstall the game. All I have done is deleted the two files listed below:

Fallout.ini
FalloutPrefs.ini

When you reload the splash screen, it will automatically go through your video settings then you can even enable mods and play the game as usual. This seems to be a temporary fix because if you exit and try to reload the game, the crash will resume, requiring you to delete the two files again and going through the video test. But for me, this has worked 100% of the time and HOPEFULLY will lead someone *Cough* Bethesda *Cough* to get a hotfix out ASAP. Please post if this has helped anyone as it has greatly helped me.