Differentiate SQL Server Express from SQL Server installed in a server
The MSSQLSERVER name in the services does not mean anything other than SQL Server (any edition) was installed as the default (unnamed) instance. It does NOT give you any information as to what version or edition it is! This can be SQL Server Express! 

You need to connect to that database instance and run

SELECT @@VERSION


to find out what exact version/edition it is.

Having the two SQL Server service entries just means you have two instances - which edition each instance is cannot be determined from their names alone. OK - SQLEXPRESS is the default name used for SQL Server Express - but you could install a Standard or Enterprise edition with that instance name - just for fun.