Eraser for U3
Eraser is an advanced security tool for Windows which allows you to completely remove sensitive data from your hard drive by overwriting it several times with carefully selected patterns. The patterns used for overwriting are based on Peter Gutmann's paper Secure Deletion of Data from Magnetic and Solid-State Memory and are selected to effectively remove magnetic remnants from the hard drive.
Other methods include the one defined in the National Industrial Security Program Operating Manual of the U.S. Department of Defence, and overwriting with pseudorandom data. You can also define your own overwriting methods. Eraser works with Windows 98, ME, NT, 2000, XP, Vista, Windows Server 2003 and Server 2008.