Hard drive starts clicking,then onboard soundcard stops working,then..

So I purchased all my components for a new build. i7 920, g.skill ddr3, corsair 550w psu, antec case, evga motherboard, eVga gtx260, wd 500gig harddrive.

Within 2 weeks of putting it all together, my hard drive starts clicking, at a rhythmic interval, say once every 13 seconds and the hd light on the tower flashes around the time the drive clicks. The clicking gets louder so I rma the drive. Install a fresh one, and this drive is silent at first, then about a week in, it begins to click as well. Within a week of that, my os wouldn't detect my (onboard)ethernet card, it would show up in the bios, and was enabled, but no device was available in windows, or while using a ubuntu live cd. I used a pci ethernet card, and I could connect to the internet again, after a week, my pci ethernet card could not be detected, but lo and behold, my onboard ethernet worked again, even though both were shown in bios and both were enabled. All of this would happen at random, the ethernet actually stopped working while browsing slashdot. So a week after that, my onboard sound stops working. I get only clicks when I try to play audio, very very low, barely audible clicks.

My first hunch at this point is my power supply is doing funky things to my other hardware. I tested my sata power to the harddrive with a multimeter and both my 12 volt rail and 5.5 volt current are easily within specs, and not inconsistent. Is it possible that the power to the motherboard is bad, even though my SATA power connector shows up within spec?

Could my motherboard be causing all of this? Any other possible culprits? Right now I have no sound and a clicking hard drive, so I'm really desperate to get to the bottom of this. btw temps are normal, and sound and hard drive do not work normally even if I shut down for hours and then reboot.