If you need the functionality of Visio 2003 without the risks, consider these modern, often free, alternatives:
Stencils and shapes that "snapped" together, making it easy to create organized layouts. microsoft office visio 2003 free portable download
Released as part of the Microsoft Office 2003 suite, this version was a major leap forward from its predecessors. It introduced several core features that defined the industry standard for diagramming software: If you need the functionality of Visio 2003