Howtogeek shows you how to overwrite free space securely in Windows
When you delete a file from the recycle bin in Windows, rather than deleting the actual file, the space the file is occupying is simply marked as free so that another file can come and use those blocks on your hard drive. One way of making sure that your data is not recoverable is to simply overwrite all the free space with random data. To do this click on start and open an administrative command prompt.How To Overwrite Free Space Securely in Windows
