I am deploying a wpf application that requires sql server 2008 as a prerequisite. As a result I am embedding the sql server installer in my application. When that launches the SQL Server Installation window shows up:

I don't want the user to have to go through out this installation. That program will install SQL Express and many other things like SQL Management Studio.
Is there a place where I can download SQL Express 2008 the database engine only? so that the user will just have to click next, Agree, Ok... etc... without having to make complicated decisions. Or maybe is it possible to install sql server express throughout the command line?
I am including the installer in my application because my application is supposed to be able to be installed without having an interenet connection. Also I cannto seem to find a place where I can download SQL Server express the database engine only.