Need Visio 2003 drivers for SQL Server 2008 with instructions

My questions is pretty simple and complicated at the same time. I need Visio 2003 drivers for SQL Server 2008 but please don't just give me a link, and tell me that I can download them from there. Explain to me exactly how do these drivers work, and are they doing for me in SQL Server 2008. I have no idea where to get them, so please give me some step by step instructions and details about there. Thank you for your help.
