If I understand your post corerectly, it sounds like either your gateway router or XP box does not know howto route packets to 192.168.1.0/24. i.e. via 192.168.0.2
You can test this on your XP box by typing (at a command prompt):
E:\scowles>route add 192.168.1.0 mask 255.255.255.0 192.168.0.2
If the above works, then update your gateway router so that it knows about the stub network (192.168.1.0/24), then when your XP box tries to access this network (without you manually adding the route), your gateway router will send an ICMP redirect back to the XP box; which will then add this network to its route tables automatically.