The FirstClass Client for Windows for 3.5 is a 16bit App, so any 32bit version of Windows up to Windows 10 should be able to run the client straight away. 

However if you are running any version of Windows 10 X64 and Up, or get an error when you try to run the installer that windows can not run this app, then you will need to launch the installer in the folder "otvdm-v0.9.0" - NOT the one that says "install (no console)" just the installe named "install".

This is a genius app by a cool person that allows Windows version that aren't able to natively, - to run 16bit Applications.

The install takes seconds, - literally and once installed you only need to run the 16bit apps you're trying to run as you would any other program. 

Once this is installed, you can run the FirstClass installer in the Folder "FCWIN350".  

There are further instructions, and a settings file for the Starlight server in that folder. 

- Sysop