Cannot ping Ubuntu and windows

[satish_j]

A big Hi to all as iam new to this forum.
Iam facing network issue with my windows and Ubuntu systems.I have connected an Desktop machine(having Ubuntu) and Laptop(xp) with a crossover cable,but iam not able to ping either of the IPs from any system.
Both the systems are in same subnetmasks.network card also says that it is connected(after connecting thro crossover cable)
Any help really appreciated..

[rcgreen]

Are they connected to anything else besides each other?
Did you assign IP addresses manually?

[satish_j]

No,there is nothing in between.THey are directly connected thro cross-over cable.And Yes,i have assigned IP addreses to both.ON ubuntu,i went to system-->Administration-->Network and assigned it the IP and gateway.
Moreover,i can ping localhost on ubuntu,i can ping 127.0.0.1 also,but cannot ping 10.16.9.81 which is the IP of ubuntu system.
Any ideas why ubuntu is not pinging to its own IP?
Also,i need to specify one more input.I have 2 NICs on Ubuntu desktop.One is using DHCP to connect to ISP and other is what i have given the IP manually and is conected to XP laptop.