I bought a new HP computer with MS Vista Home Premium and am trying to network my old Dell Windows XP Home. I got the network working with HP's help. But HP tells me that for the network to work, I have to turn-off firewalls on both computers because it is a MS Vista issue. They seem to be right because when I turn off the firewalls, I can access folders from both computers and share printer. But when I turn-on the firewalls, neither computer can...