Thanks Deed, it's really appreciated. Based on others' accounts of the Xonar working with BF2 in 5.1 i'm tempted to try reinstalling Vista.. But obviously a bit reluctant.
Just installed and tried Rapture3D, unfortunately it didn't work in giving BF2 surround sound (still in Stereo unfortunately). But it did recognise the correct speakers in the 'Speaker Layout' device (i.e. the sound played correctly from each individual speaker.
I'll play more with it to see if I need to force it in some way.. My over-riding hunch though is that I have an OpenAL problem, hence trying to find a tool to test it.
I've had a look for such a tool and couldn't find one, i'm sure something exists though. There is a reference to an OpenAL Compatibility Test app online, but the link was removed (I even registereed on the forums and checked their download section with no luck).
Edit: Thread i'm on about is here
http://www.frictionalgames.com/forum/thread-1677.html
EDIT2: I've reinstalled OpenAL numeerous times but it all points to a problem somewhere along the way.. Bearing in mind that the OpenAL imitator in the ASUS Xonar Control Panel (DS3D GX) doesn't work for me in any driver install i'm beginning to wonder if something is missing and that's what's causing the problem.~
HSmgr.exe and HSmgr64.exe both exist and are running, so it's activated..
EDIT3: Sorry to ask again guys, but is the SoundEngineTest program in the Battlefield 2 folder functional?