Strange behavior of ASP.NET 4.0 Application with SQL Server 2008

Hi I don't know how to define my problem but let me try: I have developed an ASP.NET 4.0 application on visual studio .NET 2010. Then I deployed it on Windows XP. The application uses Database from SQL Server 2008. SQL Server 2008 was already installed on windows XP. I attached the DB from my application, created a user for db and used the following connectionString in web config.

connectionString="Data Source=PC-Name;Initial Catalog=DataBaseName;User Id=username;Password=password;"

The application is now working i.e. It is querying the database but when I try Insert Operation it gives the following error:

开发者_高级运维> Server Error in '/' Application.
--------------------------------------------------------------------------------

A network-related or instance-specific error occurred while establishing a 
connection to SQL Server. The server was not found or was not accessible. 
Verify that the instance name is correct and that SQL Server is configured to 
allow remote connections. 
(provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) 
Description: An unhandled exception occurred during the execution of 
the current web request. 
Please review the stack trace for more information about the error 
and where it originated in the code. 

Are you sure you are using the same connectionstring for that insert operation?