SqlDataAdapter error

In Visual C# 2005 express, I´m trying to use an SqlDataAdapter object, but I obtain the following message from the "add connction" window after clicking "test connection" button:

"...server does not respond...,or server is not installed "

I use sql server express and the database was created with sql server management express.

thanks,

Marco Leòn

some code like what the connectionstring says and .... would prob be a good thing to share with people