Do you have Comgenie's awesome file manager? If you do, on the left side go to hdd0\game\blus30337 (If you are in America)\ patch_mp.ff (only highlight, dont click)
Then go to the right side and go to usb### (# will always be different mine is 000) go to you patch, click on it untill you see Patch_mp.ff Highlight that and then press (Circle), (Start) and it should copy, start up mw2 and go to private match and you should have your mods menu. Hope I helped!! sorry if a bit confusing... =)