Challenge Unlocker Problem

well. i used this hack -> http://www.mpgh.net/forum/404-call-d...or-v3-1-a.html
and clicked the wrong one 'unlock all challenges' or something like that and now all my challenages are unlocking really fast and im ranking quite fast.. can i stop this in any way ?

You can delete all your .STAT files and then use the hack again to get back to whatever level you want. I don't know where the .STAT files are but i guess they are in the game folder and then "players" folder.