Multiple Default gateway in win xp

Hi,
In my office I have 2 internet routers.
i.e 192.168.0.1 & 192.168.0.2 wired & wireless.
All the pcs on the network are given 192.168.0.1 as default gateway. If there is a breakdown on the 192.168.0.1 then the users are not able to connect to the internet. I have added 192.168.0.2 as additional gateway in all the pcs.
What cud be the problem. If I change the default gateway to 192.168.0.2 then it connects.
I want the pcs connect automatically if there is breakdown to the second gateway.
Help pls.