Griff Palmer, of the San Jose Mercury-News, reminded us today of something called a "DOD-compliant wiper."  (Yeah, yeah.  Hold your jokes.)  These software utilities are intended to really clean data sets from hard drives.  Why do we care?  Read this piece, "Hard Disk Risk," by  Simson Garfinkel wherein he does the equivalent of HD dumpster diving.

But here's the related message from Griff Palmer:

"Here's a by no means comprehensive list:

http://buy.cyberscrub.com/csutility/compare.html

I used an evaluation copy of BC Wipe and found it very easy to use. After installation, you can right-click on a file and choose "erase by wiping" from the pop-up menu. It does the ostensibly DOD-compliant wipe on the
file and also on the virtual memory.

If you're serious about the subject, Peter Gutmann's seminal paper on the topic is worthwhile reading, particularly the caveats about achieving secure deletion from journaling filesystems (which NTFS is, I believe) and RAID systems:

http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

If you search for "5220.22-m" and "dod 5200.28-std" you can find information on software that claims to meet the standards. The search will also turn up lots of technical info on the standards, themselves."