Never had this, but there's two things to try: 1. Start Steam as Admin and launch TSC once. Then start Steam normally. 2. If issue still persists, delete or rename the "installscript.vdf" from the RailWorks folder - it's only needed on first start anyway. Not sure why Steam triggers it everytime for you. You can also try to go to the RailWorks\Install folder an run the setup exes manually. (vcredist_x86.exe, DXSETUP.exe, PhysX_9.10.0513_SystemSoftware.exe) and see if there's an error message.