In Windows Vista, you have BitLocker protection that enables you to secure the contents of your hard disks against anyone who might try to read the data on disk. However, there might be times when you want to make sure that nobody can possibly retrieve data from your hard disk. While BitLocker is an extremely effective measure, it's still possible that someone will be able to get your PIN or password and USB key. For example, someone might threaten your life or the lives of loved ones if you don't give them what they need to access your hard disk.
If you need bullet-proof protection against data leakage, the best way to do it is to destroy your hard disk. But that's hard to do -- suppose you're at the airport and you can't let snooping authorities inadvertently leak information about your next IPO, or attorney/client information, or doctor/patient information, or PII stored on your hard disk that could get you into major regulatory compliance issues if you give over your encryption keys.
So how do you destroy you hard disk without creating a nuisance? You use a "Dead on Demand ENHANCEDHARDDRIVE" by Ensconce Data Technology. These work by imbedding a destructive chemical inside the disk casing (assumed to be some sort of acid) that physically destroys the hard disk platters. There's no way data will ever be retrieved after the platters are destroyed by acid! Ensconse claims that no other component of the computer will be harmed. So, as long as you have a disk image handy in a safe location, you can just get a new disk and apply the image to it and you're good as new!
For more information, check out: http://www.deadondemand.com/products/enhancedhdd/