The detection on the analog ports simply monitors for some kind of impedance, and from the impedance guesses what is likely to be present.
I think, as well as discovering the cable that was never connected to the F_Audio, you may have another cabling error in there. Assuming you have front and rear audio connectors, I'd check they all go to the right place. In addition, somewhere on the Realtek > device advanced settings check whether you have "mute the rear output when a front headphone is connected" (I'm working from memory) deselected. I guess a mis-wiring on the fron ports might mute the rear ports otherwise.
Did you note where I said the rear audio connectors probably can't, depending on the motherboard, drive speakers directly? They'd need powered speakers or an amp. Maybe if you're plugging speakers in directly you're causing the system some problems.
OK, I looked at the manual: the rear audio connectors are on the back panel (duh...) and you've now connected the front audio. Do headphones work or not in the front audio jack (front, as in front jack on the case, not as in front set of a surround system)?
Read some more: the outputs on the back are line-level, so they won't drive speakers directly without barfing.
And... a third edit. Just in case, the motherboard header marked "speaker" is for the tinny PC case speaker, not for any kind of external audio.
In BIOS, HD Audio should be "on" (but I believe that's the default). As you said you don't have an "audio" tab, I'd check it all the same.
Last edited by Bushfiva; 19th April 2010 at 00:37.