that could be a small handful of things. could be a bad connection between the disk and the motherboard, could be a bad connection between the disk and the power supply, or the disk could just be dying all together. I've been through several computer supply refreshes and we always had a few that came with bad sata drives ootb.

Try this, and see if your disk is ok: http://www.seagate.com/ww/v/index.js...00dd04090aRCRD