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.