Actually COD4 uses Directsound, not Directsound3d, hence no EAX. COD1 and COD2 used EAX, but not COD4.
Also, to clarify, EAX is only usable without resorting to annoying work-arounds (Alchemy) on Windows XP and earlier OSs.
It will still sound better on a good sound card though, sounds great on my Forte.
I use a Forte as well but game exclusively on Steam.
Here's some related info regarding EAX implementation.http://forums.steampowered.com/forums/showthread.php?t=730366