I have been trying, with the help of two knowledgeable sons, to set up a simple network , with just a crossover cable, between two laptops, one running XP and one running VISTA.
After several hours work, including disabling firewalls, sharing drives etc, and starting from PING, it was possible to see some of the VISTA drives from the XP, but not the other way round, except seemingly at random, after a reboot.
But both work OK on the wireless router to the Internet, so I have resigned myself to using the modern version of sneaker-net (i.e. USB sticks).