Two vista laptops, both set up the same one will network the other will not

Three computers; sharing problem, two are Vista one is XP Pro, one Vista will network with the XP and the other vista will not share with either. The vista’s network set up are the same. File sharing, net work name?

I think adminastrator persmission problem?

or

Security wpa2-personal (public)

or

Firewall, which I have disabled with no result.