1) Download and install CoD4
1a) Create a new profile if u allready had 1 and close the game
2) Patch the game to 1.6
3) Patch the game to 1.7
4 Use the Level 55 hack from here https://drive.google.com/file/d/0B4nlEE6LyDLqbnFUcUNkWGNXVVk/view?resourcekey=0-6ObTwpQvHq_-0HmYOZX9fw
(Download and open that file, create a folder somewhere in your cod4 folder, place the easyaccount and the playerstats together in 1 folder).
5) Run the game and check the bottom right corner if it says 1.7
6) If its 1.7 use ALT+TAB to go out of the game but the game is still running
7) Open Easyaccount.exe and press the 1.7 and click easy upgrade
Alt+Tab back into the game and if u check RANK u will see that u are level  55
9) close the game and patch the game to 20.1, download it here --> https://www.gamepressure.com/download.asp?ID=77534

If u now join our server it will be fine and u are level 55 and have all weapons etc.
That cheat is allowed as i for example reinstalled this game 20 times and i dont want to start over all the time :P.

Good Luck, any questions just post it here