ipconfig ipconfig /all in VISTA XP Pro.

Go to the Start menu and type command in the box.
Then right-click on Command Prompt and
click Run as administrator.
If a User Account Control window pops click Continue.
At the C:\> prompt type ipconfig .
Then press Enter.
Your IP address, subnet mask and default gateway
will be listed..
If your IP address is 192.168.x.x, 10.x.x.x,
then you are receiving an internal IP address
from a router or other device.
The IP address that the internet sees is that of the router.

[color="RED"If you get a 169.254.x.x address,[/color]
this is a Windows address that generally means
your network connection is not working properly.

If you want more detailed information about your
network connection,
Type ipconfig /all at the prompt

Para two : For XP
Start click RUN type cmd then OK.
A window will open
type ipconfig /all