SQL server 2008 Installation media

HI all,

I am trying to install SQL server 2008 express, and in the "SQL Server Installation Center" i select "New SQL Server stand-alone installation or Add features to an existing installation" After selecting that option a window pops up and prompt me to "Browse for SQL Server 2008 Installation Media"


Now, what exactly is "SQL Server 2008 Installation Media"? how am i suppose to locate/browse the installation media on my computer?

i am totally new to SQL server and i am self-learning it from a book, the problem is that the book does not explain where to browse for instillation media!

my system info:
Windows 7 Home premium
64-bit OS
AMD 2.60 GHz
6.00 GB RAM