4D1 Help installing

Hello I got banned from MW2 using liberation wiht UAV hack steam and someone said if I got banned to use 4D1 so how do I use it and do I have to buy it? And can somone explain what 4D1 is?

thanks my mpgh helper =D you guys are all ways helpful

---------- Post added at 11:56 PM ---------- Previous post was at 11:43 PM ----------

Allright man I have another problem I install 4D1 and now it says "Select the Modern Warfare 2 game directory." what do I select now?