I just can not get WEP or WPA working with my wifi modem in Linux
(Mandriva). If I setup a VPN (Virtual Private Network) between my main PC
(home) and the second PC in my home that has the wifi modem (on second
floor in my home) [without WEP or WPA encryption], couldn't the VPN
security substitute for the lack of WEP/WPA encryption? I have ssid
broadcast turned off, and MAC filtering on, that is the best I can do--
but of course that is easily hacked-- so I figure setting up a VPN tunnel
should provide a secure communication, correct?

Also, with an open wifi system, even with VPN, what is the risk of a
hacker using the open wifi to hack into my box (PC)? Is that possible or
made easier compared to a wired communication (LAN cabling), even with
firewalling and a router, etc? Any ways to minimize that?