Okay, okay, if dumpster diving is coming into question here...
About five years ago, I found a dumpster out front of someone's house in a neighborhood I lived nowhere near. It was about nine in the evening, nobody was awake nearby. I got curious and started digging through it. Inside the dumpster was an entire HP desktop computer. I had no tools with me, but it was easy to crack the thing open and root around in it.
I wasn't able to do much inside the case, but surprisingly,a few choice parts were not secured with screws. I think the machine was about six years old at the time, so the video card was an old Radeon, the RAM was not worth taking, etcetera. But there was a PCI wireless card (I couldn't get the screw undone with just my thumb nail so I just stole the antenna from it) and the hard drive, which was mounted with plastic tabs that were designed to make it easy to pull. I nabbed the drive and closed up the case before I left.
When I got home, I booted the nearest computer into a Linux live CD and hooked up that hard drive with a USB enclosure, and here is where the evil part comes in. Rather than doing the Lawful Good thing and simply formatting the drive, I poked around. I checked the Program Files, the Users, even the browser cache. Sadly (maybe), I found little more than a couple of cached images from a short Facebook session. The machine's previous owners had evidently wiped and reinstalled Windows on the computer before tossing it.
The hard drive in question? 40 gigabyte Seagate Barracuda. Hardly worth using even now.