You can get a list of running processes with their information

public static string ListAllProcesses()
{
    StringBuilder sb = new StringBuilder();

    // list out all processes and write them into a stringbuilder
    ManagementClass MgmtClass = new ManagementClass("Win32_Process");

    foreach (ManagementObject mo in MgmtClass.GetInstances())
    {
        sb.Append("Name:	" + mo["Name"] + Environment.NewLine);
        sb.Append("ID:	" + mo["ProcessId"] + Environment.NewLine);
        sb.Append(Environment.NewLine);
    }
    return sb.ToString();
}

The only method (That I know) to see if the process is opened by user or system is to check it s owner. If it s system, then it s not run by user:

//You will need to reference System.Management.Dll and use System.Management namespace
public string GetProcessOwner(string processName)
        {
            string query = "Select * from Win32_Process Where Name = "" + processName + """;

            ManagementObjectSearcher searcher = new ManagementObjectSearcher(query);
            ManagementObjectCollection processList = searcher.Get();

            foreach (ManagementObject obj in processList)
            {
                string[] argList = new string[] { string.Empty, string.Empty };
                int returnVal = Convert.ToInt32(obj.InvokeMethod("GetOwner", argList));
                if (returnVal == 0)
                {
                    // return DOMAINuser
                    string owner = argList[1] + "\" + argList[0];
                    return owner;
                }
            }

            return "NO OWNER";
        }

For the list of opened files, It is possible to do using Managed Code which is somehow hard. Here is an example on codeproject demonstrating the same matter

You can have a list of running processes with Process.GetProcesses(): http://msdn.microsoft.com/en-us/library/1f3ys1f9.aspx But you can have the file they have open if they exposes some automation interface you know.