Undelete software recovers deleted data by taking advantage of the way files are deleted by the operating system. When you undelete a file on Windows 7 or any other version of the OS, the logical links to the item are repaired, making it available to your applications. Also known as data recovery software, these applications can only restore data if it has not been overwritten by new information. You need to act quickly and use the software as soon as you realize that data loss has occurred.