2 Nics and setting preferred route to net

Hi,

I've got a machine with two NICs.

I'd like to set a preferred route to the Internet via one of the NICs and for the machine to only use the other route when the first one is unavailable.

I've set the Route Metric for the 'Backup' Route to 2 and after a reboot the machine appears to do the right thing and packets travel via the correct NIC.  However after a few days the 'Backup Route' gets used.

How can I force the Primary Route?

C:\Documents and Settings\Administrator>route print
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 02 e3 03 e3 ba ...... NETGEAR FA311/312 PCI Adapter
0x3 ...00 a0 c9 c8 08 27 ...... Intel(R) PRO Adapter
===========================================================================
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0       10.10.80.1      10.10.80.2       1
          0.0.0.0          0.0.0.0      192.168.0.1     192.168.0.6       1
         10.0.0.0        255.0.0.0       10.10.80.2      10.10.80.2       2
       10.10.80.2  255.255.255.255        127.0.0.1       127.0.0.1       2
   10.255.255.255  255.255.255.255       10.10.80.2      10.10.80.2       2
        127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1       1
      192.168.0.0    255.255.255.0      192.168.0.6     192.168.0.6       1
      192.168.0.6  255.255.255.255        127.0.0.1       127.0.0.1       1
    192.168.0.255  255.255.255.255      192.168.0.6     192.168.0.6       1
        224.0.0.0        224.0.0.0       10.10.80.2      10.10.80.2       2
        224.0.0.0        224.0.0.0      192.168.0.6     192.168.0.6       1
  255.255.255.255  255.255.255.255      192.168.0.6     192.168.0.6       1
Default Gateway:        10.10.80.1
===========================================================================
Persistent Routes:
  None

Thanks