SQL Netowrk Interfaces, error:26 - Error locating Server/Instance specified.)

Hi,

I have made a installer of My Windows Application (C# 2005 Express) and ported my software to a different computer. my installer installes SQL Server 2005 Express in the target machine at first then copy my software. When I installed the software in that computer and I clicked to run, I got the following error message and Program shut down.

.........................................................................
An error has occured while establishing a connection to the server.
When connecting to SQL Server 2005, this failure may be caused by the fact
that under the default settings SQL Server does not allow remote
connections. (Provider: SQL Netowrk Interfaces, error:26 - Error locating
Server/Instance specified.)
..........................................................................

Would you please guide me about this problem. Why it is looking for remote connection, It is not something like ASP.NET connecting thru Website or something like that. it is the very mdf file which is already available in the same PC and it should be accesssible thru the connection string I programmed in the application, right

Thanks and regards
Emran