Make sure you have Network Discovery and File Sharing turned on in the Network and Sharing Center on the Vista machine. Probably wouldn't hurt to turn Media sharing on as well. Do you have a 3rd party firewall installed on either machine? If so, be sure to setup an exception(rule) to allow a connection to your Vista machine. You may have to setup each machine to allow the inbound and outbound connection. I don't know what else would cause it to not work. I've been running Vista on my desktop PC for several months and I've never had any issues connecting to it from my Laptop running XP SP2.