Yes, you can build your own personal video recorder (PVR) and here's a step-by-step do-it-yourself article that shows you how it can done without breaking the bank.
Sal Cangeloso took a small form-factor Mini-ITX case and even though it had just a one-gigahertz processor with 512MB of RAM on its motherboard, was able to turn in into a PVR by upgrading it with a 250GB hard drive, beefing up the power supply to 120 Watts and installing the Ubuntu 5.10 distribution of Linux. The key to the system is the Hauppauge WinTV-PVR 350 using MythTV PVR software. Cangeloso was able to plug his digital cable right into it, and it even has a remote.
He set it up with super quiet fans and says the thing runs very well. Downloading scheduling information from the Web, he ends up with a tiny, quiet, cheap PVR that he built himself. Neat.
Mini-ITX Part III [XYZ Computing]