A follow uo - - bought new computer with windows 8.1 last April, and spent a year trying to get MSTS to work on it. It wouldn't install directly from the CD's, so I partitioned the HD and installed win 7 on the partition. Again it wouldn't install MSTS from the CD's. Removed partition and set up a virtual HD and installed win7 on it. No luck - wouldn't install from CD'S.
Downloaded and installed "Open Rails" directly on Windows 8.1, and set up all my routes as "Mini-Routes", and it works perfectly- better graphics, and more realistic train operation. Activity Generaor and Activity Master work perfectly as designed.. and this Train Driver is now happy. If you want to learn how to set up Mini Routes, I will be happy to show you by email.

smokeytc69@gmail.com

Happy traindriving.
Ted