Building an HTPC on the cheap is not about the hardware, but about getting the most out of the hardware you have purchased. You can build an HTPC with Athlon FX 60 or a Pentium III 700 MHz. The only rule that remains constant among HTPC's is that they are in some way able to record and playback TV. For some, this is on a 70" HDTV and for others, a 15" analog monitor will do.
Building a cheap HTPC is not about building the cheapest thing that connects to a TV, but building the cheapest HTPC you're happy with. This article describes not what cases and CPUs to choose, but the cheapest way to interface your chosen rig with both you and your television signal.
Free PVR software is not about sticking it to Bill Gates by not spending the extra $40 for Windows Media Center Edition (MCE), or some other similar application such as Snap Stream's BeyondTV or Sage TV. All of these offer similar services for about the same price. Free PVR software is about customization. Examples are:
When most people see a system that can do the above, they react in one of two ways. They're either shocked at how much time you wasted or they think that it is cool. If you're still reading this article, I assume you're in the second category.