HOW TO RESET RANK
1. Make sure MW2 is closed.
2. Go to C:\Program Files\Steam\userdata\some#'s\some#'s\remote and delete all the files there.
3. Go to C:\Program Files\Steam\SteamApps\common\call of duty modern warfare 2\players and delete JUST the "STAT" files there.
4. Load up MW2 and press play. Make sure your Rank is Lvl 1 and you should be good to go.
NOTE: THIS WILL ERASE YOUR CLASSES, RANK, CHALLENGES, CAMPAIGN, STATS, and SPECIAL OPS MODE!
THANK ME IF I HELPED!
If you need help just post it (in CLEAR English) in a reply!