Cannot connect to Windows 2000 Server

I am having problem to get access from client pc’s (Windows 98, Windows 2000 and Windows XP) to Windows 2000 server. This only happend if I’m in the different segment with the server segment. For example when i’m try to get connected from windows xp client pc, i can see the server name but if i’m 2x click it, nothing appear in the next window. I’m already upgrade to win xp sp2. If i’m using windows 2000 and windows 98 to find the server, nothing appeared. Please help. Thank you.