NT as router :please help asap

[Sandy Green <sand232 () yahoo com>]

I have a issue going on with NT box, which is acting
as a router. It is a Ethernet based LAN.

This is the configuration.

                 Cisco Router
                    |
                    |
                Interface 1
                    |
                NT BOX
                    |
                Interface2
                    |
                    |
                   PC A

> From cisco router I can successfully ping Interface 1.
PC A can successfully ping Interface 2. Problem is
that
from cisco router i cannot ping Interface 2. However
from PC A i can successfully ping Interface 1 and 2.
Ofcourse IP forwarding has been enabled on the NT Box.

I have simplified the configuration for the basic
issue.
If anyone would know why the NT Box is behaving like
this.
This is a switched environment. 
Please respond asap as i am pretty much stuck.

thanks




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