I had problem with playing Fallout 4 on MSI GT70 with Intel HD4600 and Nvidia GTX970M onboard. Nvidia optimus technology was not switching between HD4600 and GTX970M when i was running Fallout 4. Now everything works fine and smooth even if game launcher in options still says "Low Details". Just override to Ultra and its good.

What to do? I found that optimus is not switching between GPU's when game is in 64-bit mode and working on Windows 7 64-bit (dunno if this happens on other Windows).

How to fix it? Need to make one small correction in registry key.

Open windows registry and look for a key:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows]

then look for "RequireSignedAppInit_DLLs" entry on the right side of window. The value of it is probably 1 (dword:00000001). Just double click on the name and change the value to 0. Restart PC and try to run Fallout 4.

For me it worked with all 64-bit games.