Whenever I try to run dreamseeker, I get a system error message which says "The program can't start because d3dx9_43.dll is missing from your computer. Try reinstalling the program to fix this problem.".Reinstalled about three times, still get the same message.
The d3dx9_43.dll file should be installed as part of the DirectX redistributable that's included in the installation package. If you're installing from the .exe, not having that file shouldn't be possible.

That file was missing from the redistributable in early builds of BYOND 509, but since then it's been present in all of them.
Download directx 9 from microsoft.