Whilst my system was running (Windows 7) the whole system just crashed (no blue screen just an immediate reboot) and the HDD the OS was on disappeared from my system (meaning not detected by BIOS, not actually physically disappeared).
I have another HDD and my motherboard has a few free SATA II slots. So, I tried plugging my broken disk into another slot, swapping the SATA cables between the broken disk and the working one (which always shows up). Disconnecting the working disk and using the power cable from that disk in the broken one, but the broken disk always fails to show up. Well, it did a few times but then the system just crashes again, and now it doesn't turn up at all.
When the broken disk did appear on the system I booted SystemRescueCD and got an extended SMART scan to complete: absolutely no problems. There were also no reallocated sectors, no pending sectors: everything of any note was zero. The only thing even resembling a "problem" was the relatively high disk temperature of 44C, but that's not even that bad.
So, any ideas on the problem? The fact that the other disk works fine precludes a PSU or motherboard problem, unless I'm missing something. So it must be the disk. But the SMART scans indicate it's not a problem directly related to the platters or the needle, right? It goes without saying that I will ddrescue the data off the disk, but my question is really this: do I need to get a new HDD or a new motherboard/PSU, or something else entirely? What else can I do to isolate the problem?