Originally Posted by
Luke122
Are you attemping to bridge the networks? IE, use the wifi on the laptop to share internet to the desktop through the crossover cable? If so, make sure DHCP is enabled on both ethernet adaptors, and enable "internet connection sharing" on the laptop.
Also, on the Vista machine, you might need to ensure that your network type is set to either private or work, since public will prevent the vista computer from being seen by the XP computer.
Try turning off the firewalls on both to see if you can ping each other.