It sounds like authentication mode of the SQL server is set to 'Windows Only'. You can change it to 'SQL Server and Windows' on the Security tab of server properties in Enterprise Manager.

>Hello all. I'm pretty much a novice when it comes to SQL server. I've written a few simple stored procs & UDFs in t-SQL, and I'm using ADO.Net to work with the data. This is porbably a simple fix but I haven't been able to figure it out yet.
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>I had to reinstall windows & SQL server, and now I can't log into my local server using SQL authentication. Even using SA and blank in Query Analyzer, i get the following message:
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>Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection.
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>I've looked all over MSDN for help, all I find are some pages on ASP.net & ADO that refer to this problem. I can log in using Windows authentication just fine.
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>What am I missing? I'm sure it's something simple. I've already checked the server logins and the database users and everything looks fine there. I checked those settings against another installation of SQL server on a different machine, and they're identical.
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>Thanks in advance for any help.
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>-Nate