Yep, ipconfig will dislpay any info you want about your connection and you can release / renew your ip address but only if you have a DHCP server running. You cant change your ip manually with ipconfig.

The two ways I would probably do it is either:

Double click on your connection monitors in your system tray > Properties > Internet Protocol (TCP/IP) > Properties and then select Use the following IP address and fill in the fields with the relevent information.

The other way is to use netsh as has been sugested

Open a comand prompt and type netsh you sould then get the netsh prompt.

Then type the following:

set address name="[Your connection name]" source=static addr=[your ip] mask=[Your mask] gateway=[your gateway]

So it would look something like the following:

set address name="Local Area Connection" source=static addr=192.168.0.10 mask=255.255.255.0 gateway=192.168.0.1

The benifit of this way is you can write a small batch file to allow you to do this pretty quickly, just double click on it and you away!

Im sure there are other ways but these are just the two I use!

You can find more info on netsh at Microsoft