How to back up user profiles in Call of Duty 4?

This is a guide on how to keep your user profile data intact in COD4 when you want to have them on another system or when you change your OS.

It's actually quite simple:

I - First, make a copy of the user profile you wanna keep. This is how to do it:
1 - Go to you COD4 installation folder (for example it may be C:\Program Files\Call of Duty 4 - Modern Warfare)
2 - Now go to players folder and then profiles.
3 - Here you can see one folder for each user you have created.
4 - Enter the folder of the user which you wanna keep and copy it's contents somewhere safe (by content I mean: config.cfg, config_mp.cfg and mpdata)

(Caution! if you have new profiles on the new COD4 and you want to keep them too, things get a little tricky. There's a way to keep them too but, come on already, let them go!)

III - In the new installation of Call of Duty 4 create a new profile, if you haven't already, and then go to Options -> Multiplayer Options -> Enter Key Code section and enter the same key code that you had for your old profile (the one that you want to port into the new system).

IV - Now quit the game. Go to COD4 installation folder and then players folder and then profiles folder. Here, create a folder with any name you want. This will be the name of your new profile with the same settings as the old profile. Finally, copy the files that you backed up to this folder (i.e. config.cfg, config_mp.cfg and mpdata) and you're done. Just start the game and enter the profile. Voilà! it's all there!