Dual NICs interferring problem

[xz157cng]

I have a 8 years old computer that run XP Pro. There are two NICs-
NIC1 -> internet
NIC2 -> router -> another network
Both NICs are enabled. Lately, NIC1 drops communicating when
NIC2 is enabled. NIC1 works fine when NIC2 is disabled.

NIC1 TCP/IP property is set to obtain IP address automatically.
NIC2 TCP/IP property is set to 192.168.1.68, mask 255.255.255.0 and
with a default gateway no.

What would cause this problem now after 8 years? Any recommendationns?

 

[xwb]

What are the address ranges for NIC1 and what is its subnet mask?

Is it possible to change the DHCP range for NIC1?

If they are both 192.168.1... it is possible that when the DHCP lease was renewed, there was a clash.