installing and configuring sql server and IIS for asp.net 3.5 database app [basic]

I'm very sorry about this being a very cliché question, but I really need to understand some specific things.

Everytime I add an sql server database in visual studio 2010 it creates a database under App_Data and then the connection string the server explorer uses is one which has an AttachDb field that points to the file.

Now when I tried that on 2 IIS servers 6 and 7.5 I had a slew of errors saying the user

"An attempt to attach an auto-named database for file XX failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share."

if I use this format "Server=\sqlexpress;Database=xxx;Trusted_Connection=True" I get

A network-related or instance-specific error occurred while establishing a connection to 开发者_StackOverflowSQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections.

I spent a whole day trying all kinds of different connection strings, configurations, and combinations!! =S

My question is : What is the RIGHT way this is to be done? Should I make the database in sql management studio 2008 R2 express? What KIND OF connection string do I need, and what config do I need on SQL SERVER 2008 R2 Express IIS Windows Server 2003 R2?

seems I need use the integrated security(windows authentication) connection string, also I had to use localhost\sqlexpress instead of .\sqlexpress. For IIS 7.5 an app pool login needs to be added into sql servers logins!