My friend has a WDC5000BPVT, just today he found that his laptop wouldn't even show a POST screen.
He took the hard drive out, and the laptop started working happily (also works with other hard drives plugged in, just not the WD). I put the faulty hard drive into a SATA-USB bridge, worked just fine, passed tests from WD's WinDLG tool. I put the hard drive in my laptop, and it worked just fine.
So it seems that laptop suddenly decided it didn't want to work with the WD hard drive. What gives? I have no idea how to troubleshoot this.