SDelete is a secure delete application that can overwrite a disk's unused or unallocated space, or securely delete existing files. It implements the US Department of Defense clearing standard DOD 5220.22-M, and you can specify the number of overwrite passes it makes. It can also wipe Windows NT/2K compressed, encrypted and sparse files (it uses Windows defragmentation API to accomplish this), and clears the NTFS Master File Table (MFT). (It does not delete the filenames of your files in the free disk space though - apparently it is not possible to do this in NT/2K.) This program comes with source code and works under Windows 95, 98, NT 4.0 and Windows 2000. It is a command line utility.