In Need of Understanding...

What is the difference between the AC97 & HD Audio cables? And do I need to connect both into the mobo for onboard audio?

I have a CM Stacker 830 and the AC97 cables are many and not sleeved very well.

i think the HD cables transform digital information and the ac97 is analog signal.
soooo you should connect them both

You only connect 1, and this has to do w/ your front-mounted audio plugs which are very optional. If your mobo has support for HD audio in the BIOS, then you can plug in the HD Audio plug, and enable it in the BIOS. If not then it should say AC97, and you should hook it up that way. If you don't use the front-mounted audio plugs then you can leave these disconnected.