Ah.. actually that's a clever way of performing diagnostics.
At least in XP I seem to have things as good as they'll get... mostly. Half-Life is definitely doing occlusions, which is a 2.0 feature but it's really hard to tell if it's doing wavetracing since that's a combo off occlusion and reverb and neither are very pronounced at distances.
Unreal based games are totally not working for me right now. In DX, underwater sounds the same as above and every voice seems to be direct from the source. I've screwed with the ini, put dlls in the game folder... I dunno. Something was working once upon a time but now it just sounds like D3D. I get the same generic sound in Anox, Unreal, UT99 and DX.
With space games like Tachyon or Starlancer I basically have no clue if anything is working. In all cases, everything detects just fine in the setup utility and then it sounds fine playing the game but since there are no walls anywhere I'll be damned if I can tell what's actually different about it.
Halo sounds like it's trying to work but failing in the process. Enabling A3D sounds like ass right from the menu music, when things get quite muffled. Any sound coming from behind me sounds muffled and destroyed, cortana's helmet babble is the same and there are stuttering glitches every so often. However things ahead of me sound pretty good so something is working.
I did what you said and put audio3D 2008, a3d 2009 (audio3d 2009) and a3dapi 225 in the system directory except for halo's game dir having the newer one. That got me where I am above.
98 is another story. It's the only OS that will play certain things like Q3 stuff. 98 was working even better until I tried to install VXD drivers (because I didn't think I had that version but I actually did) and now the damn speakers won't go into 5.1 mode. This is another problem I ALWAYS have: That software responds randomly based on nothing. Sometimes redoing the exact same setup will break everything that was working for no good reason. I can't tell you the number of times I've redone the same damn procedure with different results, on all sorts of things, especially Creative products. So now I guess I'm going to have to reinstall the drivers yet again just to get my 5.1 back. I wish I just had a disk image where everything works. Doing forensics on retro audio has its appeal and novelty factory until it doesn't. Now it's just a pain in the ass.