My father-in-law just upgraded his home PC and bought an Audigy 4 Pro along with Logitech's Z-5500 5.1 surround speakers. Upon getting them set up they failed to produce correct surround. Everything comes out of the front speakers only.

I haven't been able to get over there yet but tried helping over the phone for several hours one night and got nowhere (I'm in the sound industry so this isn't new to me so it's somewhat unlikely that it's some sort of newbie setting that got overlooked.) We tried disabling Creative's CMSS3D, their Dolby decoder, everything everwhere is set correctly to 5.1, etc.

What's most frustrating is that he called Creative twice and both of the reps said, "Oh, those are digital speakers and won't produce 5.1 output with our sound cards." WHAT?!?!?! No f'ing way. I called and got a similar answer. We then both called Logitech and Logitech reacted almost as if they weren't sure they even sold speakers. In other words, they were no help what-so-ever.

I simply find it impossible to believe that one of Logitech's top speaker systems simply do not function with the most popular name in sound cards. It just makes no sense.

Can anyone help or point me to another resource where lots of people might be posting that might have some ideas?

If he's trying to hook them up thru the digital input, he's out of luck. Actually, you're lucky to get any sound at all, since most creative cards ship with an incompatible, proprietary digital jack.

Use the 6 analog lines to hook them together, should have no problems.

I think that Klyith is right, if it's true that you connected the speakers digitally.

the SPDIF PCM signal cannot contain more than a 2 channel signal from the front speakers, and i think the logitech system is doing some pro logic processing, aiming all mono sound at the center channel... (maybe a setting somewhere can change that)

If you want 5.1 channel sound, the signal needs to be DTS/DD encoded, which is the case when playing a DVD. Some sound cards, like mine nVIDIA nForce SoundStorm 2 is able to do a live-encoding of the 6 channels to Dolby Digital, i'm not sure if your Creative card also can do that...

Hook up your Audigy4 to your Logitech Control Center via TOSlink/Coax.

Start -> Creative -> Audigy4 Pro -> Audio Console
Select Decoder -> SPDIF Passthrough
Select SPDIF -> Enable Bit Accurate Playback

On your Logitech Control Center, select Input: Optical
If you're watching a DVD with Dolby Digital 5.1 encoding, you'll be able to experience surround sound. Otherwise, select Effect button until you see [Dolby Logo]PLII Movie. Your 2ch audio stream will be mapped against Dolby Pro Logic2's matrix and outputs a simulated surround, whcih is pretty incredible. Try it with MP3 audios.