I was wondering that myself. I just did a free upgrade to Windows 10. When I was using Trainz Build 49922, it worked just fine with Windows 10. It's when I started using the higher builds past 49922 that the problems began, I have Railroad Simulator Powered by Trainz 12. The system requirements are: Windows 7, Vista or XP, 3.0 Dual-core processor, 1.0 gig of Ram (I have 8), Video card 512 MB, I have way more than that.