Windows route table

There are to network adapters within my Desktop. The routing table is always malfunction after I connect two different subnet. I have no idea to set the static routing table in my Windows XP, so I manually write a batch file to clean routing table and add correct default route rule.
FYI:
tryfix.bat
route -f
route add 0.0.0.0 MASK 0.0.0.0 172.21.0.254 METRIC 20
ipconfig /flushdns

Route rule fields are as the table below:

Network Destination	Netmask	Gateway	Interface	Metric
0.0.0.0	0.0.0.0	172.21.0.254	172.21.3.51	20