The proving_grounds.zip file you have requested: Maps Levels Missions / Map Packs / Proving Grounds - 27.24mb 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:
PROVING GROUNDSNOT FOR CE!!!!!!!!!!!!!by: hunter_cool_grunt_chickenEnter an arena were so many elites have fallen to earn their ranks.This both versions include 1.Shadow Warthog2.Moniter Odd Ball3.Capture The Sword ( LOL :P ) The map comes with 2 maps for the dowload of one! The first is an arena style map for Halo Pc only. The second version is the same map with AI enabled, just for you loney people.