I'm looking for a program (freeware is good, but I'll pay for something I value) that will do a zero-write (US Gov't quality) to the un-used portion of an otherwise in-use hard drive. I don't want something that will wipe my entire drive, I just want to wipe the un-used portions of the drive. Basically like Norton's file shredder, but rather than drag-n-drop files, I want it to automatically zero-write the un-used portions of my hard drives.