Business has become increasingly dependent on the Internet and computing to operate. It has become apparent that there are issues of evidence gathering in a computing environment which by their nature are technical and different to other forms of evidence gathering, that must be addressed. This paper offers an introduction to some of the technical issues surrounding this new and specialized field of Computer Forensics. It attempts to identify and describe sources of evidence that can be found on disk data storage devices in the course of an investigation. It also considers sources of copies of email, which can be used in evidence, as well as case building.