How do I use Halo Custom Edition on my flash drive?

Alright. Here's the deal. I own Halo: Combat Evolved on my PC. I installed Halo Custom Edition and it works flawlessly without any errors. What I want to do is be able to play Halo Custom Edition from my flash drive on any computer. I placed all of the Halo Custom Edition files on the flash drive and brought it to school. I attempted to launch it but the error that came up said "Invalid CD key". I want to game to be able to access all of the components needed for it to properly run on a single flash drive. Could I somehow put my registry file into the flash drive and have the game read it from there? I don't really want to have a hacked version of the game that doesn't require a key. I would just want to be able to have the game read the key off of the flash drive without me needing to install anything on the computer I plug it into. Any help would be appreciated.