multi network adapters????

wish that i will find someone who will tell me how can i find this problem...

im working on a program that used socket programming, and its working between two pc's, where each pc has JUST ONE NIC, but when i add a second one, it cause delay to responce.

if i disable it, the program in that side will return working normally.

is there a way to set a default NIC if i have two???

also i tried to view my IP's, using
VB Code:
[Highlight=VB]Dns.Resolve(Dns.GetHostName).AddressList(i).ToString
[/Highlight]

and i got two ips, which are assigned for the two nic's, i tried to change the order, but seems that its a read only array, anyone know please how to sellect the wanted ip, and put it in the index Zero, cause it use the first index in the first try to send anything from local machine

any comment please