modding new maps

[killzone2k3]

i would really appreciate someone helping me try and mod the new maps. I dont want to put halo2 on my hardrive because i use it for othe things(apps etc.). So i would really appreciate some help. I have tried modding with all the different map editors and then resigning them and putting them back on my hardrive but it says that they fail to load. I know alot of people have posted on this same thing but all the solutions came back to putting halo2 on ur hardrive and i dont want to do that. Thank u for just reading this post and maybe someone can help me out.