Here is a method to release and renew your computers local ip address from the DHCP server quick and easy.
Click Start ,search for cmd and open cmd.exe (if you use Windows XP then click on Run instead of typing in the search box, and if you use Windows Vista then right-click on cmd.exe and select Run as Administrator.)
Now type the following ipconfig /release and press Enter
When that completes then type ipconfig /renew and press Enter
Type Exit when done to close cmd.