What is the Server name for SQL Server2008?
The server name (and instance name) for SQL Server Express by default would be localhost\sqlexpress (or .\sqlexpress, or yourMachineName\sqlexpress, or x.x.x.x\sqlexpress, where x.x.x.x is your machine's IP address).  That is provided two things:


You on the machine that houses the database engine
You kept the defaults for SQL Server Express installation to make it a named instance, named SQLEXPRESS


As for the login.  Most likely if you just installed it, select Windows Authentication and try to connect.  I'm guessing you have added your account as SA priv.  Did you create an sa account during installation?  If so, and you enabled Mixed Mode authentication then you can log in with the sa credentials you created initially.