Complex version that might give better results
1) Goto
http://code.google.com/p/namebench/downloads/list and download namebench for your operating system (mac or windows) its a small program only 5mb odd
2) Run the program and you should see it has entered your details ie, location, browser ect (make sure these are correct if not change then in the drop down menus Make sure that Include best available regional dns services is checked, then hit Start, it takes about 3-5 mins to run the entire program so sit back twiddle thumbs till it finishes.
3) Once it has finished it should give you a list of the fastest DNS servers in your area , with the highest showing a percentage increase on speed in the top left hand box, don’t worry about any warning messages you get to do with hijacked domains in the list ect as we aren’t changing your browser DNS only the xbox.
4) Top right hand box will show the primary and secondary DNS sever IPaddresses for the fastest DNS server it found.
5) Turn on your console and via the dashboard open up the system settings tab and scroll down and click onto Network settings
6) Select the connection you use and then press configure network
7) You should now have a screen that is tabbed basic settings with the DNS setting at the bottom, scroll down to the DNS settings and press A
8) Chose “manual” and the screen will now show two options primary and secondary dns servers
9) Highlight primary , press a and enter EXACTLY the ip address for primary shown in namebench in the top right hand box (then press start button to confirm)
10) Highlight secondary, press A and enter EXACTLY the ip address for secondary shown in namebench in the top right hand box (then press start button to confirm)
11) reboot xbox and away you go.