Ignore that last post, i figured it out. If anyone else wants to use it as a referance... u can just delete the Userdata files, and the connon files.
(This will Reset all Challenges, Unlocks, Stats, Kills, Deaths, ect, This will make it so you Never played the game yet basically.)
All files in,
Steam\steamapps\common\call of duty modern warfare 2\players\
Sorry for the spam o.O <3 mpgh ftw.