Darik's Boot and Nuke

DBAN - Open Source Data Deletion Tool

Darik's Boot and Nuke (DBAN) is an open source erazer software designed for consumer or home use. Also known as DBAN; it is a great tool for wiping the contents of a computer you're selling or as a way to ensure you've eradicated all viruses and spyware before doing a clean OS install. However, users should be aware of its limitations, especially for larger environments such as a company or organizational network.