HTPC hardware issue

So here's the deal, I recently (back in Feb 09) decided to build a HTPC (Home Theater Personal Computer) and at first it worked great! Now it is F-ed. I am looking for help where people are willing, here is the skinny: When building it, I used the following hardware:

• DVD (LG)
  
• Hard Drive (WD 1TB)
  
• Thermal Compound
• Case, MoBo, Power Supply (shuttle)
  
• Processor (2.8 ghz intel)
• RAM (2gb Crucial 1gbx2)
• TV Tuner (hauppauge hvr 1600)

I got the computer, built it and all was well. I was using Windows Vista Ultimate (trial version) and that worked awesomely, everything was going super. I left the machine on at all times, and let it sleep when it ws inactive for > 3 hours. Then out of the blue, the computer started dying every once in a while (usually at night time, and I found it dead the next morning, no I didn't have any jobs set to run at night aside from windows update)

So I do some debugging and figure its the HD, this was 'confirmed' by the memory test running 10 times all turning up positive, along with seeing the following message on the bios screen "SATA Drive 1: Bzbzbzbzbzbzbzbzbzbzbzbzbzbzbzbzbz...bz"

So I contact NewEgg and (as always) they exchange it for me with no problems. 1 week later I get my new HD, and re-install everything (same setup as before). After about 2 months, the same thing happens, and I get the nice old friendly "Bzbzbzbzbzbzbz" again. Once again I test everything, and while running my good ol' friend Knoppix, it shows that there is no hard drive... fucking super.

So I sent out and got ANOTHER HD (3rd one) and install linux (www.linuxmce.com) a distro of kbuntu and it is not even instaleld for a day or so and the Bzbzbzbzbz begins... so obviously, something is F-ed In the A somewhere else on the machine.

So the question is how do I start going about debugging this fuck-fest? If you can think of a way to help i will give you... um... a virtual hug.