Shredder is a small, free and powerful Windows gadget that will permanently and completely wipe files dragged and dropped on it.
Shredder doesn’t claim to be perfect, although it uses a powerful algorithm, however you can be sure that it will give you at least more safety than the default Windows delete option.
Take care when you use Shredder, because there is no undelete — your files can not be recovered. You should use it only when you have to make sensitive data disappear completely. Note also that Shredder works only for files named in Latin characters (file names in Greek, Cyrillic, etc will be ignored).