If you have an old VB6 (Visual Basic 6) application that uses SQL Native Client via ADO for connecting to Microsoft SQL Server you must be aware that Native Client dll discontinues the name from SQL 2005 to SQL 2008. Therefore the application raises the error: Provider cannot be found may not be properly installed.
Here is the link: http://msdn.microsoft.com/en-us/library/ms131291.aspx. The Sqlncli.dll becomes Sqlncli10.dll, this means that you should recompile VB6 or, better, install also the Native Client package for 2005: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=d09c1d60-a13c-4479-9b91-9e8b9d835cdc&displaylang=en (Microsoft SQL Server Native Client).
If you find out other solutions or this solution doesn’t work for you please left a comment!