After upgrading from Windows 7 to Windows 10 I experienced an issue where launching FONV caused the system to run the detect hardware action. It set the graphics settings to high. Clicking “Play” then caused the check to initiate again and it set it to high again. This repeated indefinitely.
Despite hunting all over the FONV / Nexus / Bethesda forums etc I was unable to find a fix, but some further tweaking cured it.
To fix the fault:
1. Locate the folder “This PC / Documents / My Games / FalloutNV”.
2. Right click > Properties.
3. Click the Security tab.
4. Click the “EDIT” box.
5. In the top window make sure your logon profile is there.
6. If you don’t see your logon profile click “Add”, type your name in the bottom box of the popup, click “Check names”, click “OK”.
7. Once you see your profile, click it and set all the checkboxes in the bottom window to “Allow” except “Special Permissions” at the bottom.
8. Click “Apply” then Ok/cancel back out.
That should fix the issue for you; it did for me!
albowyn 