well that web page is example on how to set your computer to static ip it wont set it static for you.
My advice is to get your computer working with dhcp the got to run type cmd and press enter
now type ipconfig/all
write down your info
got to control panel network connections
right click the network connection your making static select properties
select Internet Protocol (tcp/ip)
enter in all of that data manually and it should work
an easier way might be to set it static from the router
that is how I do it.
Ok I think I understand you problem now. Once you have the port forward set up correctly if your connecting to his computer accross the internet you need to connect with the modems internet or wan address. I usually don't use windows remote desktop I use realvnc but the concept is the same. If the modem is constantly changing address then you have to set up a no-ip.com account to create a web address to direct you to his IP as well as install a program that monitors the changes in address.
You need to ensure that your friends ISP is providing a Public IP on the connection, if not your wasting your time. You dont have to statically assign an IP to the desired machine on the LAN, most modern ADSL router will allow you to statically assign an IP to a machine on the LAN using the name of the device or using the Ethernet Address (physically address of the network card).
Also; in your original posting the network card settings were imcomplete; you must enter an IP Address, subnet mask and default gateway and at least one DNS.
Set DHCP to your network card (as per brw02005), do the IP config /all and write down all the details, then go into the network card and set them manually into the appropriate fields. However; to prevent an IP conflict in the future on the LAN you will also want to manually set these details in your ADSL router. This coupled with the port forwarding and enabling of RDP on the macine itself should give you what you are after.
Is your computer and your friends XP computer on same LAN? If yes, then you can use Microsoft default RDP tool with Dynamic IP Address in order to establish remote connection. If you are trying to establish remote connection over internet, you need to use various remote support services such as logmeinrescue, gosupportnow, GoToMyPC etc.