Sharing network from guest into host?

[mattn]

I suspect this is either impossible or dead simple, but either way I haven't figured it out. I've got a USB wireless thingy that I can stick up high in a window to pick up a network that my Mac can't connect to with its internal wireless. This USB thingy is a Netgear that only has Windows drivers. I can connect via the Netgear dongle from my XP guest without a problem. Now what I would like to do is share internet access back to the OS X host. Is this possible?