In order for you to play Trainz Simulator 12 on Windows with minimal graphics settings, your computer must meet the following requirements
Operating system:
Windows XP SP3 / Vista / Windows 7
Processor (CPU):
Pentium D 3.4GHz (or equiv)
Memory (RAM):
1 GB RAM
Hard disk space:
16 GB of hard drive space
Video:
nVidia GeForce 7200/128MB or equivalent
Sound:
DirectX 9.0c compatible sound card
DirectX®:
DirectX 9.0c