Being secure on public WiFi

I need to connect someone's computer to an unsecure WiFi network in a public place. What do I need to do to make sure the person's computer is secure and no one else on the network can see any of the files? Also, this person has two computers they want on this wireless network and they want to be able to share a printer. So how can I make sure both computers are secure on this public WiFi network, but also allow them to share a printer? I'm sure I could figure it out after a couple of hours, but I'd rather not waste my time messing around with these computers. Two of the computers are XP and I'll probably need to hook up a third which is a Windows 7. To be honest, that Windows 7 computer is pain in the rear. It's so different from XP that I have trouble navigating through all the networking/file and printer sharing options.

 

as a minimum use a firewall and if possible use VPN, ssl to login to sites. AV enabled of course. As you get more familiar with Win7 you'll see how much easier is to setup using wireless

 

What about using Himachi/LogMeIn between the two computers?