As you know, in 1.0 the game does not support custom maps.
I create a small file, you just have to download it, extract it in the folder of your game, and launch the file install.exe
This will install the map in the folder of your game, you do not lose your level in game.
22.214.171.124:1045 [AR51] Nuketown 1.0 By WWW.AR51.EU
http://ar51.eu/cod4.zip Download this file and extract it to the folder of your game