I got a little nostalgic when I surfed around and found Fleet Defender Gold (CD Rom version) and bought it for $60. Should I have gone for the Steam version instead? Is it possible to get it to work on Win 8.1 64bit without DOSBox or is it a must to have DOSBox for it?

I have the CD version as well and need to use Dosbox to play it on Windows 7 64 bit. Since you have the CD version, you also have access to the training and supplemental material (Flight Deck, etc) included on the CD, but you won't be able to access it on a 64 bit OS. However, it can be run in XP if you can install it virtually.

Running the CD on XP will also enable you to edit the audio configuration and enable Roland MT-32 playback -- this edited file can be copied from XP and added to your 8.1 installation.

Thanks for the answer. I'll look in to it