Do you utilize file sharing and printing? If not, leave it alone. There is no reason for the computers to recognize each other if you are not going to utilize it.
If you need printer sharing to work, tell us here in the topic. There is a workaround that I know to get XP and Vista printing together.
If you need file sharing to work. I have not tried it with XP and Vista computers but I'm sure someone in the forum knows how to accomplish it so post it here.