If you don't know by now that Windows doesn't really delete files when you delete them, it's time to learn the truth. Fact is, Windows just removes data from the file system when you delete it; the data remains on your disk until it's overwritten by new data. Until then, it can be recovered, and it can sometimes be recovered even then. CyLog's CyberShredder is a free tool that securely deletes data and wipes its traces from your disk. It overwrites deleted files with random data to make deleted files unrecoverable. Although this tool is extremely easy to use, it includes a good HTML-based Help file. Its advantage is its utter simplicity; with a drag-and-drop interface and few settings, taking out the trash is no problem.
As we noted, CyberShredder is a very simple tool, with a small dialog for dragging and dropping files into. It has few options beyond several shortcut locations, always-on-top, and auto-exit when invoked with parameters. Another option enables a Confirm File Deletion notification; we selected this option, which makes you click OK to confirm that you want to delete the data in question.
The documentation recommends selecting this option when using CyberShredder for the first time since it really does wipe data thoroughly, even on the lowest of its three shredding levels. You can disable the option when you get comfortable with the tool or when you're deleting batches of stuff by simply clicking the Settings menu. CyberShredder always asks for confirmation whenever you try to delete a Hidden, Read-Only, or System file, but it will definitely delete critical files, so be very careful how you use it.
CyberShredder quickly and thoroughly obliterated the files and folders we dragged into its maw, even with the single-pass Very Quick method, which simply overwrites data with zeros. The Quick Shred method used three passes for more security; the default Normal Shred method uses 7-pass NSA overwriting. CyberShredder also uses low-level Windows API routines to override normal disk caching and ensure that every file write operation goes directly to the disk, making it impossible to recover data.
From CyLog Software:
CyberShredder is a quick, safe and handy utility that lets you erase confidential files from your computer permanently. Normal file deletion will remove a file's directory entry and allocation table information. The actual disk clusters that contained the file's data remains intact on your hard disk and can be recovered later. CyberShredder overwrites the space occupied from a file with random data and erases the file, so an unerase utility will never be able to recover it.