unreachable SQL Server for a group of computers I'm deploying SQL Server 2008 Express in my company. I already installed, did a application, tested, gave permission to user.

All desktop users run the program without any problem. But the notebook users can't establish a connection with SQL Server.

Facts:


Notebook has permission in the company's network (already access network drive)
Notebook pings the computer with SQL Server.
I gave permission for the company's groups and explicit for notebook users
Firewall and Anti-virus is turned off in SQL Server computer.


Any idea?


  System.Data.SqlClient.SqlException (0x80131904): 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)


EDIT: The problem was that the notebooks wasn't in the same domain.
This sounds like a network problem; if the other remote clients can access the instance then it seems unlikely it is an instance-specific problem.  


Be sure that firewalls on the notebooks are turned off or (better) are allowing TCP traffic through the port your server is using.
If you are connecting using the server's host name or machine name, make sure it resolves to the correct IP from the notebooks.  Try this from a command prompt on the notebooks:

C:\&gt; ping my.databaseserver.com


or

C:\&gt; ping OUR_SQLSERVER 


In the output the IP address to which my.databaseserver.com/OUR_SQLSERVER resolves will be displayed.
See if you can connect directly via TCP to check for misconfiguration of the SQL clients.  On the notebooks, type this at a command prompt:

C:\&gt; telnet 192.168.1.200 1433



Substitute your SQL Server's IP and the port it is using.  The reply you get will not be readable, but unless you get a message like Could not open connection to the host, on port 1433: Connect failed, you are at least able to connect to the server.

Hope this points you toward a resolution.