how to see active users W7?

I have a dual boot W7/Ubuntu laptop.

First question: My understanding is that an application can create a dedicated username and run under that username. For example, if console user "y" starts application a, the application may create a user named "application a" and run as that user. I have applications that want to run as "administrator", which I understand is like root in Linux. Is what I have said correct? When you look at properties of a folder, you typically see a number of users and groups (e.g. SYSTEM, Administrators, Users). I did not set up these groups that I am seeing on my machine.

Second question: Is there any way to see all the active users in W7 at any given time? How can I get control of what users and groups can use this machine?

 

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4648: A logon was attempted using explicit credentials

PsLoggedOn