Unlike XP Vista requires you make shares and allocate
them to users. (Could be only on the Business Version-Not Sure)
You do this via right click computer and manage (users)
You may want to turn off IPv6 as well as it has issues with
routers that do not cater for it.
I use Vista Business but i imagine Home Premium is no
different.
Network sharing was quite easy for a chage.
If it still gives you grief try disengaging the firewall 'till
you get the network up.
Also on the XP machines try serching for your computer
name and also ping your IP address to maake sure the
vista machine can be seen over the network.
Cheers.
Any Society That Would Give Up Essential Liberty For Temporary Security Will Lose Both & Deserve Neither.