Sql Server Db SQL Server 2000 DB Attached In SQL Server 2005 Express Not Connecting To VB .NET 2003 Application Now. WHY ?

SQL Server 2000 DB attached in SQL Server 2005 Express not connecting to VB .NET 2003 application now. WHY ? - sql server db

I had a B / W with Visual Basic. NET 2003 and SQL Server 2000. Now I have uninstalled and installed Visual Basic 2005 Express and SQL Server 2005 Express. I joined the old database (in SQL Server 2000 creates excellent) with SQL Server 2005 Express and successfully. But when I created the executable of my application (in Visual Basic. NET 2003) does not connect to the database suceessfully. What could be the reason and what should I do to solve it? ... Thank you, Zain.