Thoroughly delete sensitive data

A free tool (donations accepted) that is very robust and allows you to wipe free space (more accurately called “unallocated clusters”) as well as slack space (also called “cluster tips”) is Eraser. In addition, it includes the ability to configure your system to wipe the page file at shutdown. It includes a scheduler to allow you to schedule how frequently you would like the program to run. It is a well-designed and easy to use application.