Thanks for the help!
Ok, it's called [Application name] 5.5 Server - [Application name], and under log on as it has .\[a username related to application name]
sqlcmd -E returns:
"Named Pipes Provider: Could not open a connection to SQL Server [2]. Sqlcmd: Error: Miscrosft SQL Server Native Client 10.0 : A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections."
Ironically that's exactly what I can't do :-D. I'm just going to Google it.
Exactly the same thing happens whether I'm logged in as me (local administrator) or that username mentioned above.