how to split audio?

I'm a bit of a newbie, and wondering if anyone knows how I can split the audio? I have a dimension 9150 that I want to keep audio on my existing pc speakers, as well as run audio to my HD-tv as I create pc home theater. In my older computers it was easier because the 'pc audio' port was just one connector. But with my current Dell there are 3 inputs for audio. any advice on how to do this?