Well, my harddrive is a Western Digital and I have a never ran any diagnostics.
I have one of the Sandy Bridge motherboards (you know, the faulty chipset ones), and being the lazy pile I am, I haven't moved the harddrive to one of the unaffected SATA ports. Any idea if that would be the issue? I am not at home right now, so I won't be able to do anything to it until Sunday night.