Workgroup network - Anonymous

I have five computers in the network, all identifiable, and another one, called Anonymous. I have two workgroups, and Anonymous is in both of them.

I connect all computers either wirelessly or wired through a router/modem wireless.

I have zonealarm and firewall, wpa password set on router/modem.

Then after 30 or so minutes, anonymous disappears!?!?

What is the possibility of this being a ghost? I never had this pop up until recently. Did virus check and nothing came up. I'm concerned someone may have hacked into my account.

I recently installed Windows XP Black on one of my PCs (pirated), and sometimes I wonder if people who create these pirates can have access to your computers?

Remove that copy/delete and Use genuine Windows XP OS from your CD. Turn off the XP Black from your network what happens if you do that?