I personally can't imagine why you'd want to, but the guys at Hardware3D show you how to hook up a car audio system to your PC. I guess the current generation of multimedia speakers designed for the PC market just didn't "kick tha bass" enough for these guys ;)

"Let me warn you, the process is not easy. It requires basic electrical knowledge, and lots of persistence to accomplish; for myself, this guide took a good two hours to follow, but it may vary from person to person, and depend on your available tools."