Here is a guide on getting the files on your already jtagged system and preparing it for hosting MW2 lobbies. Yes, this guide is assuming your system is already jtagged, if you need a guide for that check the Internets.

ALL OFFLINE:
1)Install xexloader 0.26
2)Run XeXLoader and Create a folder on the root of the drive called "Games" then in that directory create another folder called "MW2" go into that folder and select "Copy DVD"
3)Replace original Files with modded ones in MW2 Directory(Make backups of originals first!)I strongly recommend putting your DVD Drive to stock firmware after you installed MW2
4)Get the latest Title Updates from this site XBOX 360 Update Center and place them in "Cache" folder found on the root of the HDD, copy the files over with xexloader.

ONLINE:
5)Reboot xbox with CAT5 cable, Log into live. If you have XBR3 it will ask to update, Dont be afraid and DO IT.
I dont even have my R6T3 removed and it only updates the data you dont have, it will know you're already running 8955 and only add avatar support.***
If you already have Avatars you most likely dont have to do this***

OFFLINE:
6)Load up xexloader and run MW2 from the menu, then go into Multiplayer and at that point you can connect to Live.
If you have the original MW2 disk I would strongly recommend having it in the drive even though you aren't playing from the dvd, just for live check I cant guarantee you wont be banned but you need all the luck you can get

TIPS FOR HOSTERS! Never EVER use your actual gamertag, use one that will only last 2 days, then make a new one for 2 days, rinse repeat.

+REP

PANSLABS