Instructions
How to fix Fallout New Vegas (PC) vertical and horizontal mouse sensitivity
1. Go to DocumentsMy GamesFalloutNVFallout.ini
2. Find [Controls] in Fallout.ini
3. Add the following to the bottom of the section
fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0
4. Search iPresentInterval and set it to 0
5. Ctrl+A then Ctrl+C what is in the file
6. Go to SteamsteamappscommonFallout New VegasFallout_default.ini
7. Open Fallout_default.ini
8. Ctrl+A Ctrl+V
9. Save both Fallout.ini and Fallout_default.ini