First off, try running the game, (DONT ALT+TAB while you do this) and set the resolution to not potato and Windowed mode. This should allow you to alt+tab.
If the game outright wont start, crashes when launching a new game, loading a save or regularly during gameplay, try these things

• Start the Game on Compatibility mode for Windows 7 and or Run As Administrator
  
• If the game still crashes when starting a new game uninstall and reinstall nvidia Physx, and then restart your pc
  
• If you're running Windows 10 then having both an Xbox controller and a different type of controller plugged in then this may prevent the game from starting, or starting a new game. So if you encounter this problem please try unplugging one controller.
  
• Make sure Microsoft Visual C++ 2005 Redistributable Package is installed.
  
  
• If your controller is not working, then please try setting LegacyInput to 1 in the Wayofthesamurai3.ini file found in the game's install folder. You can edit it with Notepad
  Running DS4Windows in the background usually resolves most/all controller issues otherwise.
  
  
• If you’re suffering from slow down and other performance issues then please try setting EnableDOF to 0 in the ini file.

Solution By Cpt.AngelofDeath
Open Nvidia Control Panel /Manage 3D Settings / program settings and add Way of The Samurai 3 /

Check the section Cuda Gpu's / Use Gpu's But Dont Click Box / You'll See None Empty After Settings Complete In Cuda Gpu's None Means Use PhysX Settings CPU Click Accept And the Game should work also
Download the latest Geforce Experience and drivers

Problems with Background Music not looping

By Melankolio
Check out this post and download the files
https://archive.org/details/WotS3BGMloop
Basically, the game's loop fails so the solution is to replace the music files with long prelooped tracks from that download.

Ini File Graphics Options
The Wayofthesamurai3.ini file is found in the game's install folder. You can edit it with Notepad
You can change the following graphics options in the ini file:
EnableDOF 1=on, 0=off
ShadowDetail 0=off, 1=norma:l, 2=hi-detail
FOV Camera field of view in degrees, default 80
You can add “Adapternumber” to the ini file. This sets whether you run the game on your primary or secondary monitor. This needs to be added to the [Graphics] section of the ini file.


To increase the framerate cap, follow the previous step and in the .ini file change
LockWindowFrameRate=30.000000 to
LockWindowFrameRate=40.000000
YOU CANNOT CHANGE IT TO 60 AS IT WILL BREAK GAME LOGIC AND MAKE THE GAME UNPLAYABLE. 40 works fine and on a 60hz display 40 is very smooth as it is the midpoint of frametime bewteen 60 and 30.