airport express help please

[turbo993]

here is the deal:

i have a mirrored door drive g4 running 10.5 connected to the internet. i installed an airport card in said g4. i have a stereo in another room connected to an airport express. all i want to do is use my airport card as a "base station" to connect to the airport express and play music. i have tried turning on internet sharing (share connection from ethernet to other computers via airport) with no luck. have tried with and without encryption.

is this possible?? should i have saved myself a lot of annoyance and just bought an airport extreme base station instead of the airport card?? (that was a rhetorical question...)

please help me....

thanks!
-elise

UPDATE:

I just read the "most helpful customer review" on this page: http://www.amazon.com/Apple-AirPort-Express-Tunes-M9470LL/dp/B0002GDIII . The review is directed towards windows users, but I applied what they were saying to my situation and it made me believe that what I am trying to do is actually possible. I currently have the airport express plugged in to my router as well as my computer. I was able to get the green light to come on and the speaker selector to appear in itunes, but as soon as I tried to move the express back to our living room, it stopped working...