TDM,DM,SD,HQ,DOM,SAB,CTF

Place all files in C:\Program Files\Activision\Call of Duty 4 - Modern Warfare\usermaps\mpislabeta1.

If this directory does not exist, create it.

(If you bought COD4 from Steam, your COD4 directory is located in C:\Program Files\steam\steamapps\common)

Run the mod of your choosing. (E.g., modwarfare.) In console enter "/map mpislabeta1"