kindly suggest me to resolve this issue ...
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)
you posted this to Dynamics NAV forum instead of CRM ...
Anyways just as it says it cannot connect to your SQL instance. Get a SQL management studio and check it . Most probably you need to get your DBA too.