Tried new Windows 10 Insider Preview build 18290 and SB X-Fi Series Support Pack
4.0 but STILL NOT WORKING!
Seems after 18xxx Windows seems x-fi drivers stopped working!
As would be expected with these Insider previews, this just happens. As the manufacturer of those drivers are not going to update their drivers for every Insider build as they are no where near any final code change. Just not worth the time, effort and cost
to do this.
The only thing you can do is to report this issue in Feedback Hub so the MS engineers are aware of this, but the responsibility of drivers working with new code is up to the manufacturer. Take this up with SoundBlaster, and they will most likely inform you
that they will not bother with any Insider builds till close to RTM when the windows code has been finalized.
You should not be running Insider builds on your main working, gaming system anyhow. If you must, consider dual-booting and running a Release build that these drivers do work on. Did you even read the Insider Agreement prior to joining the program.
https://insider.windows.com/en-gb/program-agreement/