The custom_ui_tut_big.zip file you have requested: Tools and Utilities / Tutorials / Custom UI (Main Menu) Tutorial - 12.17mb is not available. Perhaps try browsing all files for the game Halo: Combat Evolved and upload any files you want to share or are missing. This is the only information we could locate:
This tutorial by dg945 will allow you to create your own main menu (UI). It does go step by step, though you may have to watch it a couple times because it goes fast.