Like they said before monitor the temps...sounds like the video card might be overheating...your gpu has the same safeguards as your cpu ..so if it overheats it will either underclock itself or shut off hence why your pc is shutting down....try removing it making sure it isn't clogged with dust and then reseat it making sure it's properly connected...try running the game and in the middle check the Temps...or check the Temps right after it crashes