Unable to connect to SQL Server in SQL Server Management Studio Express

Sir,

i have Win 7 Ultimate on my PC and installed Sql Server 2005 Management Studio Express. When i run the sql server management studio, it dosen't shows any Local server instance on Logon Screen. And if i am providing the instance manually as (SUMEET-PC\SQLEXPRESS), it's showing an error on connecting with local server. I have also checked the services in services.msc, it's showing (started as status).

any help will be appriciable.....