You can run the game using either a PlayStation 3 or Xbox 360 emulator. Method 1: RPCS3 (PlayStation 3 Emulator)
Silent Hill: Downpour ; a planned PC port was cancelled by Konami during development in 2012. To play the "full" game on PC today, you must use console emulation for the Xbox 360 or PlayStation 3 versions. Core Ways to Play on PC
To stay legal, you should rip the ISO from your own physical copy of the game.