An IP address is a unique number that your computer is assigned in order to be identified by other computers on a network. There are two types of IP addresses: internal and external. Internal IPs, which we will focus on, are given to computers on a network. For example, the first computer might have an IP address of 192.168.1.100 and the next might have 192.168.1.101. An external IP address is related to your internet connection. If you have a cable connection, your cable modem will receive a unique IP address from your service provider.

A dynamic IP address (which Windows configures by default) is ever changing. This can be frustrating and hard to manage. A static IP is fixed or 'static'. This is required for running servers over the internet and I recommend it for all computers because it is easier to manage and organize.

Before setting your IP to static, you will want to write a few things down. Go to Start and choose Run. Type type 'command' (without quotes) and hit enter.
This is the DOS Prompt. Now type 'ipconfig -all' (without quotes). Write down your Subnet mask, Default gateway, and all DNS servers. Close the DOS prompt.

Now that you have those written down, you are ready to set your IP. Go to Start > Control Panel > Network and Internet Connections > Network Connections. Right click on your internet connection and choose Properties.

Find and select Internet Protocol (TCP/IP). Click Properties. Select 'Use the following IP address:' Pick an IP address that is compliant with your router. Usually a 192.168.1.xxx will work just fine (xxx being a number between 1 and 255). Then, fill in the info you wrote down earlier. Make sure you type the numbers correctly. Click OK to close that window and then OK again to close the Properties window. It may take a minute to apply the settings.

Restart your computer. If your internet connection no longer works, make sure you typed the addresses correctly and that you chose an IP compatible with your router. Consult your router manufacturer if you are unsure.
There you go. You now have a static IP. You can run a dedicated server on this machine and do a host of other useful things.

No-IP - Dynamic DNS, Static DNS for Your Dynamic IP This site may also be of help in this area of a staic IP, check it out, maybe helpful .