Heya BlueClaws -- the game is built on Unreal Engine 4, which requires Windows 7 or 8 at a minimum.
So that would be your problem.
My apologies for not mentioning that on our itch.io page; I've updated that with the minimum system requirements now.
*sigh* Well, I've been refusing to update for a while now....guess it's about time. But yes, it would have been good to know that before paying. Thanks for responding so quickly and efficiently.
