I finally set up a home wireless network so that 2 PCs running XP and my MB can all see each other and share files. However, to do so I was forced to disable the firewalls on all three computers. My wireless router does not have a built-in firewall and I have not enabled any security key (eg. WEP) I know this question is open-ended and debatable but how important are firewalls on a wireless network and how stupid am I to leave the network open, given I do have some sensitive data? I live in a high-rise apartment building in which many others have WiFi networks. What could realistically happen?