Hot Air Expressed (part 2)

Thanks, folks, for your advice on configuring AirPort Express.
I tried many things, eventually disabling DCHP. Another thing which may be of note was that I set up a new wireless network between the AirPort Express and my G5. I am not sure exactly what did it, but the combination of my random tinkerings enabled me to play music 1) on my computer speakers, which I disconnected from my G5, and subsequently 2) in my bedroom. However, the living room was too far away to receive anything. Which was a shame because that’s where our best speakers are.
1) The computer speakers played back music louder than when they were connected to my G5. Despite the AirPort Express being plugged into a socket right next to my G5, I could tell there was a split-second delay when I switched songs, stopped or played a song, or adjusted the volume. Not a big deal – it sounded fine. The AirPort Express didn’t flash green though – just blinked orange. Strange, no?
2) Maybe it’s the layout of our maze-like apartment but the reception wasn’t that hot in my bedroom, as the powerpoint was behind a big shelf. iTunes/AirTunes found and connected to the AirPort Express; the music played, but it sounded like it was tuned into a radio station that was 0.5 points off the mark. So I used the alternative power extension cord that came with the cable set, pulling out the AirPort Express so it could have better reception. It worked. Similarly with my computer speakers, the sound was conspicuously louder.
The only thing is, now my Internet connection isn’t working, despite re-connecting my ethernet cable to the router (in the futile hope that my G5’s AirPort card could talk to the AirPort Express, while at the same time the ethernet cable connection would allow me to surf the Net). Numerous router restarts, G5 reboots, renewals of leases, and a re-enabling of DCHP didn’t work. I’m only a beginner at networking and the crappy AirPort Express instruction manual doesn’t help. The only consolation is that I know I’m not alone.
Many more late nights to come…
[Update: I read my D-Link manual again, and reset my Primary DNS address to 0.0.0.0. Now I’m back on the Net via the ethernet cable, and I’m still able to stream music to my bedroom stereo system via the AirPort connection. (Thanks particularly to Jamie for the detailed advice, which I will use later to fine tune the system.)]