I didn't make it!
i went to a site and it told me to "DOWNLOAD HALO MOD BOOT OR HMB4V1" from a link that didn't exist. I spent a while trying to download and play mods at halomods.com but no mods would work.
Halo PC Mods http://www.halomods.com/index.php?topic=HPC_Mods Halo CE Mods http://www.halomods.com/index.php?topic=HCE_Mods PPf-O-Matic(for applying mods and stuff) http://server2.download.filefront.com/fxvcfvnute+/gamingfiles/Halo/Utilities/Others/ppfomatic_version_3.0.zip Mapping Tools, for making your own simple mods.
As for how to, it's really just trial and error, I usually make my OWN mods, but you know, go for the PPF-O-Matic
And visit Halofiles.com for more help and downloads.