You'd have to unpark your CPU to get Windows to use more cores to complete a task. Even then, getting your CPU unparked to use all cores is risky; there's a chance the game and some other tasks in Windows designed to use a certain number of cores may not be too submissive to being forced to use more. This could cause random app crashing, Windows crashing, and even file corruption. So if you do unpark it, be careful. Do your homework.