Hermetic Systems' Data Destroyer is a disk-wiping utility that can render data unrecoverable by overwriting it multiple times. It will scrub your hard disks, floppies, and ZIP disks clean. It will delete individual files, whole directories, or entire disks full of data. You can select the type and number of purges, or overwrites. Data Destroyer will even estimate how long it will take to perform the selected number of purges. It meets stringent U.S. Department of Defense standards for data disk sanitization, too. If it's good enough for the Pentagon, it'll probably meet your needs, too.
Data Destroyer downloads as a ZIP file but it installs and opens conventionally. There are constant opportunities--and reminders--to purchase and register the software. The trial version has limited functionality; nevertheless, it's a simple enough program to use, and it will give you a feel for what the full version can do. The interface is clean and self-explanatory, and the trial version includes a link to the program's extensive online manual, if you need more help. The layout is simple enough that even inexperienced users can safely delete data from their systems without getting into trouble.
With cybercrime on the rise and more of our daily lives being transacted online, it just makes sense to protect your system. A good disk cleaner like Data Destroyer should be a part of your security team. Data Destroyer is free to try and $23.75 to buy. It's certified to work in both Vista and Windows 7.
From Hermetic Systems:
When Windows 'deletes' a file it does not actually destroy the contents of the file but rather simply unlinks the file from the file directory system, leaving the contents of the file in the disk sectors. This data will remain there until the operating system uses those sectors when writing new data. Until the old data is overwritten (which take months or longer) it can be recovered by programs that read disk sectors directly, such as forensic software (so called because it is used to obtain evidence in criminal investigations and also in legal discovery). In order to be sure that a deleted file really is deleted, gone for good, its contents never to be seen again, it is necessary to overwrite the data sectors of that file. Data Destroyer purges data in files, where 'purge' means to destroy, to eliminate completely by overwriting, so that the data cannot be recovered by any means. Data Destroyer allows you to destroy the contents of a file by overwriting it several times (or many times) with random bytes, and with bytes with alternating bit patterns, before the file is deleted. Data Destroyer can purge: a single file, all files in a folder, all files in a folder and all files in its subfolders, a specified subset of files in a folder and (optionally) in its subfolders, all files whose file dates are before a specified date, all files in selected subfolders (or in selected subfolders of a folder).