Run iw4mp.exe, then alt+tab and run aIW2.exe
That'll download the aiw2 files. Then run iw4m.exe (im not typo'ing anything). You might need to download the oilrig map, which is in the FAQ. That'll do it!
P.S. To get pres 10 from start
Step 1: press ~
Step 2: type SetPlayerData prestige 10 then press enter
Step 3: type SetPlayerData experience 99999999 then press enter