^ as Atif just suggested turn off any Firewall Windows setting that may be applied... Vista also has a cool feature in the networking section to basically diagnos this issue and tell you where it is... it will show you were the connection stops. If your on a small network make sure you can ping the router/switch/other machines, make sure your router/switch doesn't have you turned off for outbound traffic or has limits on how many can go out. If your on a large network there are really way too many variables, network settings, protocols, etc...