I thought that everyone destroyed their old hard drives. Any time I’ve ever gotten a new PC, I’ve first taken and transferred some of my stuff to the new PC, left all the old junk, clutter, and old emails on the old drive. I then remove the drive from the chassis, take it outside and whop it a half dozen times with a 16 pound sledge. I don’t want some trash picker taking my old PC chasis out of the trash on trash day and browsing through my old bills, documents, and personal stuff. Even formatting the drive will not remove the files from a determined hacker. You have to physically destroy the drive.
Actually, you need a program that “wipes” the drive completely clear to prevent people from snooping on the drive. I believe there are programs out there that allow you to rewrite every sector with a single type of data (government rules require you do re-write every sector three times).
That's not really true...A simple 0-write is sufficient, unless you have super critical data that someone with a couple million dollar lab really wants to get... Your average hacker isn't going to get anything off of a zero-written drive.
When I did some work at a government installation, I'll never forget how angry the manager was for having to sign off on a VERY expensive 20MB hard drive that the thought was going to be replaced under warranty, when I explained that if I didn't have a core to return to Compaq, he was going to be billed for a brand new 20MB drive from the service department, i.e. about 2x the price of buying a new one from a computer store. I offered to not do the service, but he needed the computer fixed right away, and since the computer was in a secured area of the installation, the original drive had to be hand carried to the metal shredder, and he had to watch it shredded, and sign an affidavit.
Today there are software packages that was securely "shred" your data. There are a number of good free ones that will keep most determined hackers from being able to recover any data, though shipping the drive to a data recovery house like OnTrack might be able to recover it. And if you're willing to pay for the software, you can get DOD certified data destruction. It's rumored that the "No Such Agency" can recover data once it's been wiped by DOD certified software, but nobody's saying for sure.