When you delete data files, the information is not really removed from the hard disk. Instead, the space that was occupied by the deleted data is deallocated and is available for use when new data is written to the disk. Until the space is overwritten, it is possible to recover delete data with raw disk editors and various data recovery software.

The built-in Cipher command-line utility has a special option to clean deleted data on a hard disk. To overwrite delete data, use the Cipher utility with the /w switch. Use the following steps:

1. Click the Start button and type cmd and press ENTER.
2. Type cipher /w:DRIVER:\DIRECTORY and press enter. Specify the drive and the folder that contains the deleted data that you want to overwrite.

The Cipher utility permanently removes the data. The process can take a long time if you are overwriting a large space. The Cipher utility is available for Windows XP - Vista. Windows 2000 users must install the Windows 2000 Security Rollup Package 1.