The HMT_plugins.zip file you have requested: Tools and Utilities / Map Tools / Halo Map Tools Plugins - 6.68kb 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:
Download this file, extract it, and then drag all the plugins into the HMT plugins folder. These are plugins for the halo modding tool Halo Map Tools.