I Plug in my internet for the xbox360 on my laptop & it said i cant use the same IP address??
( my bro is got 1 to btw) his is pluged in the router.

So if i buy a 360 Wireless Thing for it will that work?

the comp is 10 feet away from my 360.

Try setting up the 360 correctly to the laptop first, you may just save yourself $100.

Here's a cut and paste from my page.
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Internet Connection Sharing

1. Connect your Xbox360 to the ethernet port on the back of your computer.
2. on your computer, hold the windows key and press R (The windows key is the key with a windows logo on it, typically found between the left ctrl and alt keys by the spacebar. On laptops the location can vary)
3. A 'run prompt' will open. Type ncpa.cpl and press enter. This opens up a window called 'network connections'
4. If you have a network bridge or sharing in place already, remove it.
5. Right click on the wireless connection, click properties, then click the sharing tab on top.
6. Check the box that says "Allow others to connect using this connection. Click ok.
7. Windows will do it's thing for a few seconds and then inform you of your ethernet port's new IP address. (192.168.0.1)
8. On your 360, go to network settings. set to manual. enter the following info.
IP Address= 192.168.0.2
Subnet Mask=255.255.255.0
Gateway Address= 192.168.0.1
DNS for first server put 192.168.0.1 Leave second blank.
When you test your Xbox live connection after entering the first 3 IP numbers, your DNS may automatically set to the correct one. You can leave it auto in this case, or set it to manual to avoid any future issues.

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If you have additional issues after that, let me know.