File I/O permissions, the C# way

Those interested in the why can have a look here[^].
For now, I wonder how to do the following:

During installation with administrative permissions, my software creates a directory within "Documents and Settings\All Users\Documents". Users shall save their projects there.

Normally, users are allowed to create their own files there but not to alter files created by another user. I want to allow users to change all files regardless of creator. This is what I derived from stackoverflow.com[^]

// Create a new DirectoryInfo object.
System.IO.DirectoryInfo dInfo = new System.IO.DirectoryInfo(dirName);

// Get a DirectorySecurity object that represents the
// current security settings.
DirectorySecurity dSecurity = dInfo.GetAccessControl();

// Add the FileSystemAccessRule to the security settings.
dSecurity.AddAccessRule(
    new FileSystemAccessRule(
        new System.Security.Principal.NTAccount("UserGroupGoesHere"),
        FileSystemRights.DeleteSubdirectoriesAndFiles,
        AccessControlType.Allow
    )
);

// Set the new access settings.
dInfo.SetAccessControl(dSecurity);

Maybe, I'll have to repeat permission adaption on every file create for the newly created file. But still the question stands: What is "UserGroupGoesHere" to substitute for? It shall represent all normal users, not excluding power users.

How do I get the name of the "users" user group on any given windows pc?

Tags: C# (C# 2.0)