Visio is not comming with MS-Office 2007

Hai Friends,

I have installed the Microsoft office 2007 on my Windows 2008 environment.
But when i opened the Microsoft Office using Start --> All programs --> Microsoft Office,
ButI am not able to see the Microsoft Visio 2007 tool.
I need to use it to design some documents.

Can anybody please help regarding this as why the Visio option is not there with the Office 2007?

Do I need to change some settings to get it or is there any other tool to install it separately?