Well, yeah, I like to know how Dolby Digital in games works. What does it mean?
I know how EAX works- it simply creates different sound effects according to the surrounding.
Okay. But what does Dolby Digital do?
I thought Dolby Digital in games is somewhat impossible, because unlike EAX, it can't be
created dynamically, but must be readily mixed. However, in games where situations are never
the same, you can't mix the sound in advance, it must be created dynamically, according to the
situation and environment. But according to Dolby, they seem to have developed a new
technique to make Dolby Digital possible in games.

Well, what's the story now with Dolby Digital in (newer) games, like Prince of Persia or Army
Ops, what are the advantages?

When I changed my SB Live! 5.1 Platinum against my new nForce 2 onboard sound, I could
only hear that the sound in, for example, Army Ops sounds a bit "smoother" than before. But I
had 5.1 sound with my Live! before as well. And of course the whole sound sounds a lot better
then before (with my Live!), so I can't really tell what's the difference now.

And maybe the answer to my DD question will already answer the following question: when playing games in Dolby Digital (PoP, Army Ops), does it make sense to deactivate EAX?

Dolby Digital "in" games is just a marketing ploy. Absolutely no games feature any audio encoded in that format.

If you want Dolby Digital encoded content in games then you need to be using a nForce/nForce 2 motherboard which supports that feature - that can then encode audio into that format in real-time - which basically means that instead of needing to use 3 (analog) line-outs you can instead use 1 S/PDIF cable to connect to a Dolby Digital decoder instead.
The nForce motherboards that include this feature can do this with all audio (though obviously it's not needed if you're playing something thats encoded in that format, i.e. most DVDs).

EAX has nothing to do with this at all & if you want environmental effects in your games then you'll want to enable it (Some games tie 3D audio to this as well, so if you want that as well then be sure its on).

The "advantages" to this encoding are that you'll only need to use 1 cable instead of 3 & your receiver may well feature better DACs than the nForce (likely). On the downside dolby digital is a lossy audio format.

Thanks Thomas!
So I guess, the Dolby Digital logo in games only means that they support a 5.1 speaker set. But as you already wrote, it doesn't really matter if you connect your 'puter via one optical cable or three analog cables for the different channels, the result will be the same in the end: 5.1 surround sound.

Yeah, something like that, I forget exactly, supposedly Dolby Labs checks the 3D audio support for the game & that's it. So, far as I understand it even ancient games like Dark Force 2: Jedi Knight could be considered Dolby Labs certified Same story with Unreal - anything that uses DirectSound3D at all (In which case the Soundcard is what determines how many speakers it can support)
It's just nonsense unfortunately, it's the same thing with the Xbox as that uses a nForce motherboard as well.