Warning, I have noticed several times that during important updates of Windows (the last being the monstrous “Fall Creators Update” of December 2017) VirtualMIDISynth disappears purely and simply!
I was first alerted by my ears: the sound of my MIDI files was shitty again, then by my eyes: Karaboss player was displaying “Microsoft GS Wavetable Synth” instead of “VirtualMIDISynth # 1 “.
You have to go back to Coolsoft website and reinstall VirtualMIDISynth from scratch…