You can do this easily this way:
1. Click on your Windows Start button in the lower left corner
2. Select Run
3. Type cmd or command to open a DOS window
4. write the following text and hit enter: ipconfig /all
5. Then you will see some lines with data like this:
Ethernet adapter Wireless Network Connection:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) PRO/Wireless 3
Physical Address. . . . . . . . . : 00-13-02-42-C8-AF
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.2.2
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.2.1
DHCP Server . . . . . . . . . . . : 192.168.2.1
DNS Servers . . . . . . . . . . . : 192.168.2.1
Lease Obtained. . . . . . . . . . : 5. januar 2007 00:56:44
Lease Expires . . . . . . . . . . : 8. januar 2007 00:56:44
This is the example for my laptop wireless computer. You will have something similar for your network card for your desktop computer.
Here you see that dhcp Enabled is set to yes which means that my laptop receives a dynamic internal ip address.
You can also read the computer internal LAN IP address from the text IP Address. Mine is 192.168.2.2
The text Default Gateway will tell you the IP address you need to contact your router. Mine is 192.168.2.1
Write down your Default Gateway address and start your WEB browser. Write in the Address line of the browser the following text and hit enter:
http://<your Default Gateway>
Mine is:
http://192.168.2.1
Also notice the text for Subnet Mask. You will need it to setup your static internal LAN IP address. Mine is: 255.255.255.0
Also important to setup a static IP address is the address to the external WAN DNS server. This is not shown properly above because it shows only the internal DNS server. But you can find this value inside the router status when you open the WEB site address for the router to configure it. Just look at the text I sent you about port forwarding. If you still can't find it you can always find it by calling your ISP.
Good luck in trying and don't forget to tell how it went.