If you can get it to work, then i'd suggest selling it and getting a lower power CPU for your HTPC. i7-870 is a 125W part (I think) which is pretty power hungry and hot for HTPC purposes.
Nice find though!!!
You can under-volt and under-clock it. You don't need a ton of power for media playback, and even HD capture/encoding doesn't need a lot of power to capture 1080p in real-time with a good codec like MJPEG, HUFFYUV Multithreaded x64, or Lagarith.
Free is free and if it works, is stable/undamaged, cool. Here's to hoping the motherboard is bad but the chip is good.