No, I only have the one HDD. I've had it since 2010, Doug gave it to me when I built my PC. I do work the hell out of it, between gaming and regular use. The only other thing I can think of that might be causing the freezing is something going wrong with the motherboard, unless memtest just didn't catch something during the passes. It only makes noise on boot, but it is pretty audible.
I downloaded Seagate SeaTools, gonna give that a try and see if anything comes up there.