Problem with networking W2K and XP PCs

I have recently installed a new XP on my home lan and can’t seem to get the W2K pc and the XP PCs to see each other. I use a home router and both have IP addresses from the router. With the firewalls disabled, they can ping each other. In Network Places, the only PC i can see in the woprkgroup is the one I’m using. Any ideas?