video/sound card probs with Quake 4?

I just bought my first Apple. I got the new 24" iMac with 2 GB RAM and the 256MB graphics card. I also purchased Quake 4. I loaded the game and it runs but with no sound. Other Apps, like Big Bang Chess, have sound.

I changed the settings to Ultra High Quality and it was unplayable. Still no sound and froze every few seconds. The audio settings says my sound card is not compatible with Open AL. What is that???

I also changed the settings to 16:9 aspect and it still plays soundless with 4:3.

I had hoped I was leaving these issues behind me in the PC
world. (Unsure of my OS).

24" iMac Mac OS X (10.4.7)

24" iMac Mac OS X (10.4.7)