Have you ever noticed that copying a large file on Windows NT can take a really long time, but deleting the same file will happen almost instantly? Actually, when you delete a file, Windows simply deletes the index for the file and the file content remains encoded on disk. The space that the file occupied is not zeroed, so it's possible for raw disk editors and recovery tools to restore the file. So how can you permanently delete a file on disk? The answer is to use SDelete - another SysInternals tool by Mark Russinovich.