I also have been having the same problem on my Dimension 5100 with the audio card, I am using a soundblaster 24 live. I have tried 2 set's of speakers, one old pair of Altec Lansing with a sub, and the cheapo dell's that came with my Dimension. I know the speaker's work as I hooked them in the headphone jack of my boombox, and they sounded great, boy if I could only get that sound quality out of my computer now. I am past my warrenty period so I went out and bought another soundblaster 24 live card and replaced it, the sound came back but I can't turn up the volume without alot of distortion and hissing, All my of diognostic testing say everything is running correctly, HUH. I beg to differ, must be a default message? I have uninstalled all the driver's and software and updated with the newest driver's from Soundblaster. I did call creative labs but got more Bull. They were useless. Thats a whole nother story. Well I looked up my Primary IDE controllers and I have the following:
Primary Device 0 ultra DMA mode 2
Device 1 Ultral DMA Mode 1
and on my other primary controller
Device 0 Ultra DMA Mode 5
Device 1 Not Applicable
I am also using a western digital HD 60gig
hope this helps and I do hope to get an answer soon.