You would be able to see the service account details from the "Services.msc" tool. You can reach their by either
>> Typing services.msc from run command
>> Control panel-> Administrativetools->Services
All the available services are listed with the "startup" type and the "log on as" details. You can check the respective application ( Eg: if its sql server, check for SQL Server and SQL Agent service details to know the service account).
If you are not very sure about the respective service name, you can also see the description available on the left hand side for details.