Put them on different subnets. Try this first:
DC port 1 (10.0.0.1) → RAID port 2 (10.0.0.2)
RAID port 1 (10.0.1.1) → Win 7 port 2 (10.0.1.2)
Win 7 port 1 (10.0.2.1) → DC port 2 (10.0.2.2)
Netmask of 255.255.255.0 for everything.
I think that'll work. May need to enable IP forwarding too though (unsure).