Few days ago, my Western Digital Caviar Green(WD5000AACS) HDD started acting up. A new bluescreen every other minute. Re-installs of Windows and Ubuntu to no avail, no matter how much formatting. Diagnostics reported no errors. Wrote zeros to entire disk(a lengthy 2 hour process), and now it runs better than when it was new.
I used to boot in just over 1 minute. Now, I boot in <30 seconds.