Xbox 360 live using internet through my laptop

Make sure that your xbox account is connected to a Xbox live membership. If so go sign out, and then sign back in and it should Work.

Follow these steps if you are trying to use a laptop :
1.
Make sure that your XBOX 360 is fully functional and your laptop is connected to the internet by means of a wireless card.
2.
Locate the Ethernet cord and connect it to both the computer and XBOX 360. Don't turn on the XBOX 360 yet.
3.
On your Vista, click "Start" then "Network". After select the tab "Network and Sharing Center." On the left tab, click on "Manage network connections." You will see a Local Area Connection and a Wireless Internet Connection.
4.
Use your mouse to select both icons and right click. Click on Bridge Connections. Turn on your XBOX 360, Sign In, and you will find yourself connected to XBOX LIVE.
5.
Once you are done, and you need to use your computer for other uses. Simply right click on the Bridge Connection and select disable.

For more information on how to connect and use xbox go to the link below you will find all the details :

http://www.microsoft.com/windowsxp/using/networking/setup/xbox.mspx

I am not that much clear whether you can change your Ip adress, but any queries regarding Ip-detais can be solved here, http://www.ip-details.com/

1.Simply connect your xbox 360 to the internet with the Ethernet cable. Go from the xbox 360 to a router or directly to your internet source; internet modem or internet cable if you have fiber optic internet connection.
2. Turn on your xbox 360 and go to the xbox live tab.
3. Go wher it says Join and follow instructions.
You can put your credit card info. or buy a prepaid xbox live card

things you can do..... first start by connecting your 360 to the router and run a test through the system setting menu on your 360 dash board.... to do this go to system setting menu and select the network setting menu.... after selecting network setting there should be an option to test you`xbox live connection.... this is the first step in trouble shooting.... if your xbox connects to the network or router than the problem may be in the Internet connection.... after you have a connection between the xbox and the router... connect the router to the Internet and run the the test again... if you are connected to the network and the internet but still not to xbox live try doing a system update to update your system with xbox live.... after doing all of these steps you may have purchased and xbox that has been banned from xbox live and will not be able to join xbox live..... a more simple solution is that you may not have an xbox live account and simply need to set one up... this can be done through the xbox or you can go to www.xbox.com and set up a live account... you can also find FAQ's and trouble shooting steps there

use your computer to make a mac bridge.

i think you need to connet it to a computer with the internet

In theory you should be able to "share" your internet connection. I use a Linksys WRT54GS wireless router and I have a Linksys Game adapter on my son's 360. He has not complained about lag or slow server times unless other intensive bandwidth is being used.

This site has good information relating to connecting your xbox 360 to xbox live wirelessly with laptop or modified router and improving xbox live NAT rating:

How to connect to xbox live wirelessly

Make sure ethernet cable from XBOX 360 is connected to one of the 4 access ports on the back of the router.