Hi All,
It is SQL server connection problem. either use sql server 2005 express edition since by default, ASP.NET 2.0 uses the built-in AspNetSqlProvider for storing details about the registered users
of your application and that is SQL Server Express Edition file or connect the application to sqlserver in server explorer of visual studio 2005 by providing username and password.
if the problem still exists then re-install your sql server and the following steps:

Right-click on My Computer
Select Services and Applications
Select Internet Information Services
Select Web Sites
Right-click on the web site name and select Properties from the contextual menu
Select the ASP.NET tab
Click the Edit Configuration button
When the ASP.NET Configuration Settings popup window appears, ensure the General tab is selected.
In the Application settings area, ensure the DBConn value matches the DBConn string settings in your .NET application’s Web.Config file. If it doesn’t, highlight the DBConn setting and choose the Edit button to correct this.

hope this will solve your problem.
Enjoy.......
Arun Kumar

I dont have IIS on my computer and i'm running this using the utility in VS2005Pro. I get the same message: An error has occurred 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 Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

after reading all this, I'm still not sure how to resolve it...

I had the same problem...
and resolution?
Wrong connection string: I used
localhost instead of localhost\SQLEXPRESS

eg:
osql -E -S LOCALHOST
[SQL Native Client]Named Pipes Provider: Could not open a connection to SQL
Server [2].
[SQL Native Client]Login timeout expired
[SQL Native Client]An error has occurred 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.


osql -E -S LOCALHOST\SQLEXPRESS
1>

:) So add name of server (as shown in surface area configuration),
sqlexpress is default form XE.

what i have done that which sucessfully connect the sql server with other sql server (2000) is

i simply change the client configuration setting of the sql server in the odbc to TCP/IP on the port 1433 on my machine A. after that i am able to connect the sql server 2000 on placed on other machine with sql server 2005 express edition to my machine A.

MACHINE --->A---> CAN CONNECT -----> MACHINE---->B--->SQLSERVER2000
[CHANHGE ODBC ON THIS]

hello i am shujaat from pakistan

Thank you, thank you, thank you Ondra1
God bless you!!!

Win XP with SP2 may have Windows Firewall blocking you. Check this link out for more info:

http://support.microsoft.com/default...b;en-us;839269

I ran the application perfectly sometimes not work properly(it Shows Error 40 Network pipes..).
To rectify this, I modify the steps what ever i found in different blogs. these are time consuming....................
OMG! I loss my hair till now i didnt get the result. watz the problem.
Atlast i Found a result try this way http://www.codeproject.com/KB/aspnet/LightIIS.aspx
And
If u satisfied or found a result for Error 40 pls mail to me
praveen_asley@yahoo.com

I am agree with your answer, and its helps to those who suffering form same problem.