I just installed SQL Server Management Studio Express 2008. For the username \'sa\', I tried to change the password and login through SQL authentication but it failed.
I
Try restarting your SQL Server. Looks like the service is not accepting the connections.
Verify that "SQL Server and Windows Authentication mode" is selected in the Server authentication section of your server's Security properties.
Looks like SQL server is not properly installed.check computer>manage >services and applications ... if you can see SQL server under that its install is successful. if not the problem is with the installation