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Change your Server Authentication from Windows Authentication to Mixed Mode Authentication. To do that<br />
<br />
1. Right Click Server in SSMS and Choose Properties.<br />
2. Click Security and Choose Mixed Mode Authentication. ( SQL Server and Windows Authentication Mode)<br />
<br />
That's it.
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Hi,<br />
&nbsp;<br />
Thanks for the response. From the reinstalled computer I can access all shared folders and printers in the computer running the SQL server. I guess that is what you meant.<br />
&nbsp;<br />
Then, if I don't have a credential-passing problem, what can I continue to look for?
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First you can turn off the Windows Firewall and then try. &nbsp;Then turn it back on. &nbsp;Tell me what your results are and we can go from there.<br />

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Hello,<br />
<br />
Yes, I have also disabled Windows Firewall, but the same errors keep on happening...<br />
<br />

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The other reason that you can see this, is that it is trying to use Named Pipes and it is not enabled on the server.<br />
<br />
What are the protocols enabled on the Server side in SQL Configuration manager?
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Have you tried my comment no 23754905 by changing Authentication mode.
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In the SQL server the following protocols are enabled:<br />
&nbsp;<br />
TCP protocol<br />
Shared Memory protocol<br />
&nbsp;<br />
but name pipes are disabled.<br />
&nbsp;<br />
rrjegan17: &nbsp;I haven't changed the authentication mode on the server because it has to work as it is, with the Windows authentication. This problem only takes place after formatting one single client computer, and only happens in that computer. 
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For Windows Authentication to work properly, Enable the Named Pipes. Kindly check it out once.
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At the end the problem was a wrong creation of the user in the client computer. The shown username was &quot;Antonio Garcia&quot; in Control Panel --&gt; Users, but in the Users list ( Administrative Tools --&gt; Users) , the username was &quot;Juan&quot;. I changed the name of the user but not fixed the error. Creating the user again with the correct name on the customer computer was enough to fix the error. <br />
&nbsp;<br />
Thank all for the support and ideas &nbsp;
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<div class="content wysiwyg-content">
Hello,<br />
I have SQL Server 2005 and Windows Server 2003. Recently I formatted and reinstalled all programs of an user computer of the WorkGroup that &nbsp;could access the sql server but now when I try to access to the SQL Server from the formatted computer with the same user and password &nbsp;I get:Login failed for user ''. &nbsp;Not associated with a trusted SQL Server connection.<br />
I have the Windows Authentication in the SQL Server enabled.<br />
<br />
Can anybody help me ?<br />
<br />
Thanks in advance.<br />

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Hello,
I have SQL Server 2005 and Windows Server 2003. Recently I formatted and reinstalled all programs of an user computer of the WorkGroup that  could access the sql server but now when I try to access to the SQL Server from the formatted computer with the same user and password  I get:Login failed for user ''.  Not associated with a trusted SQL Server connection.
I have the Windows Authentication in the SQL Server enabled.

Can anybody help me ?

Thanks in advance.


Login failed for user ''.  Not associated with a trusted SQL Server connection

Microsoft SQL Server 2005 is a suite of relational database management system (RDBMS) products providing multi-user database access functionality.Component services include integration (SSIS), reporting (SSRS), analysis (SSAS), data quality, master data, T-SQL and performance tuning. It includes support for managing XML data and allows a database server to be exposed over web services using Tabular Data Stream (TDS) packets encapsulated within SOAP (protocol) requests.