Earlier quoted context omitted.
This application fits your needs on the Windows platform: "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. Eraser is currently supported under Windows XP (with Service Pack 3), Windows Server 2003 (with Service Pack 2), Windows Vista, Windows Server 2008, Windows 7 and Windows Se…
Does this properly work on a modern journal-ed filesystem? My impression of the equivalent linux utilities is that while they appear to work on modern linux filesystems, they no longer provide as much security as you might think.
(I do know that SSDs change the nature of the problem dramatically, as their internal storage allocation techniques tend to be opaque to the operating system. One cannot guarantee that an instruction to overwrite block X will be interpreted in the desired manner.)