What do you do when your HD crashes and you don't want to spend thousands of dollars on a professional recovery service? You do it yourself, and with any luck, it will work. Scott Moulton of Forensic Strategy Services went through the process of trying to pull things off a 'dead' HD, focusing mainly on a few things that are not painfully obvious. Here's an excerpt:

The first thing is that in his view, about 85% of the dead drives are due to software, not hardware. This can be fixed with a bunch of tools, mounting in a different OS, using a LiveCD, or simply trying it in a different version of the OS itself. There are tons of tools, ranging from really expensive to free to help you here, try them all if you need to.

The other 15% is mechanical, and that is where the problems come in. 10% tends to be the electronics on the bottom, 4% are the heads or platters, and about 1% is the motor. Because the PCB on the bottom of the drive is usually held on by a bunch of screws and not soldered to anything, replacing it is an easy thing to do. Physically swapping the electronics is something a beginner should be able to accomplish.

The problem is that those electronics tend to change on a regular basis, be it the PCB and components, or the firmware, and it does so without any warning. Because the drive is a self-contained unit, who cares what happens on the inside. If you are going to swap PCBs, you need a drive date coded within two months of the dead one, less if you want to be safe. Basically, if you want to do electronics, time matters.

The heads and platters that make up most of the rest are much more tricky. If you have ever opened up a HD, you have seen the heads on an actuator arm, and the platters. If you have one platter, you are in pretty good shape, you can take it out, put it in a different drive, and still have a slim chance of it working. If you have multiple platters, you can not take them out and have any realistic chance of ever recovering your data.