Every law office or government agency needs this! I just found out about a new technology that is called a Digital HardDrive Erase Shredder. It appears to be the fastest way to safely delete data from your hard drive. So far, I have only discovered one brand that has one of these on the market - HSM. Here is a bit more info that I found out about the shredder. If you know anything about them, or anyone else making them, please let me know!
A Digital Shredder utilizes “Secure Erase”, the safest and fastest technology to date, to delete the data. The hard disk is irrevocably erased and perfectly conditioned for re-use. This recycling is also good for the environment. The shredder is user-friendly, thanks to the touchscreen and the intuitive design. No need for lengthy set-up and training processes.
An eraser will remove the data from a hard drive instantly and the hard drive will be ready for reuse. The Advantages:
Here is a chart that shows the different ways that you can delete data - and why this method is so effective. 
I found a HSM DS-200 for sale at iShopShredders and for only about 13K...not bad for a large office that needs to get rid of secure documents. Any law firm or accounting firm needs one of these. Check it out 