Hellow fellow members of AO. I was scanning one of my systems on my LAN

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\cn22>cd c:\nmap-4.11

C:\nmap-4.11>nmap -sS -osscan-guess -sV --version-all -P0

Starting Nmap 4.11 ( http://www.insecure.org/nmap ) at 2006-09-30 21:46 Atlantic
Daylight Time
All 1680 scanned ports on are filtered
MAC Address: 00:04:5A:7F:E0:06 (The Linksys Group)

Nmap finished: 1 IP address (1 host up) scanned in 42.313 seconds

and I was wondering is there anyway, to block nmap from finding/displaying my MAC address from my other system? Also, how I could make this output more secure? Meaning, when someone scans that system for shits and giggles, I don't want them seeing the MAC address, or me see the results? I am currently running windows XP SP2 firewall. Both systems running XP Pro. All help is greatly apprecited.