Using MSSQL 2000 and Windows Server 2003 Enterprise running on a separate machine from the web server, I was unable to get PHP to connect to MSSQL with default Windows Server 2003 settings. I got it working the following way:

From the Windows Server 2003 machine:
Control Panel -> Local Security Settings -> Security Settings -> Local Policies -> Security Options
Set "Network access: Let Everyone permissions apply to anonymous users" to Enabled

There is probably a better way, but this works
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Manual Page -- [url]http://www.php.net/manual/en/function.mssql-connect.php[/url]
Edit Note -- [url]http://master.php.net/manage/user-notes.php?action=edit+33988[/url]
Delete Note -- [url]http://master.php.net/manage/user-notes.php?action=delete+33988&report=yes[/url]
Reject Note -- [url]http://master.php.net/manage/user-notes.php?action=reject+33988&report=yes[/url]