Ive been having a problem with crash on startup, and with this garbage, but I found that if you move steam out of (x86) as well as runing FNV EXECUTABLE in windows 7 compatibility mode, having the LAUNCHER run as admin on startup, and copying the steam executable into your FNV folder (Not changing the location, copying and pasting the executable) it should work. Its been bugging me for a good 4 hours of trying to fix this, so if anyone is still having this problem, I hope this helps.
And for the record, doing all of these seperately didnt work, so I dont know if I found the golden combo to make it work, or if I did the correct thing last so heres the order I did it in:
1. Tried running as admin, didnt work
2. Tried compatability and running as admin on startup, didnt work
3. Coppying the steam exe into the folder, didnt work
4. All 3 of the previous, didnt work
5. The first two as well as moving the steam install out of (x86), didnt work
6. All of the previously mentioned methods and it worked.
I also have a working theory as to why it happened, after seeing that my game took up a lot of space on my drive with mods, I deleted the game from file manager and took the script extender with it, as well as other mods that did major changes. Not confirmed in the slightest, but just a hunch.