Sorry, keyboard problem

Basically, the points you raise has nothing to do with network management:

1: 24hr online does not mean he/she is the admin. This person may be just like you downloading files.

2. You can create your own domain using Windows server. He is running in domain mode does not mean he is the admin.

3. Definitely you cannot join to his domain because you are NOT the administrator of that domain. You need to know the admin user name and password before you can join to that domain.

4. That is because you are NOT using Windows NT4, Windows 2000 Server or Windows Server 2003.

So, from that you are telling us, this computer may oy may be not a network administrator. To me, it is impossible to tell.