Security → [Windows] netword adsl security help

Hey folks,
i need some instructions and help on security.
we recently purchased a BIPAC -7100 ADSL Router to connect 3 pc's to the net. to find info in the BIPAC its at www.billion.com.au
i was just wondering how easy is it for my email and instant messaging like hotmail and msn to be monitored by other pc's using this kind of ADSL Router, and does its security protections such as Built-in NAT firewall

Bridge filtering via MAC address

Local password protection

L2TP/PPTP/IPSec pass through
help in anyway? if my tracks are able to be monitored by the other pc's is there a way i can avoid it? i have programs such as mcafee personal firewall, zonealarm pro and windows washer are they enough to protect me?
thanks for ur time much appeciated

Probably better asked in the security forum then in the networking forum.