2 Network Controllers and NFS-Service on Windows Server 2003 Enterprise Edition

I have the following problem:

I have two network controllers in my server:

1. IP: 192.168.0.5 Mask: 255.255.255.0 Speed: 100 Mbit/s Full Duplex
2. IP: 192.168.0.6 Mask: 255.255.255.0 Speed: 10 Mbit/s Half Duplex

So when a Linux client mount a NFS-Directory on the server through the IP
192.168.0.5 only controller one sends/receives the data to/from the
client. But when the clients mounts the dir through IP 192.168.0.6 the
request is handled by both cards.

How can I stop the first controller from handeling the request directed to
the second controller?

Thank You

p.s. the reason is the following the linux clients have only 10 Mbit Half
Duplex controllers in it and so the connection is much faster 10 Mbit/s -
10 Mbit/s than 10 Mbit/s - 100 Mbit/s because in the second case the
switch has to convert the 100 Mbit/s to 10 Mbit and this will slow down
the connection dramatically