Call of Duty 4 Multiplayer profiles usually gets corrupted once you have changed the OS or transferred your files to a new computer. This can be used to still preserve you profile, ranks and challenges, your beloved red tigers and bling bling weapons.

• First, copy your Keycode. Then get your profile files in these location:

The following are where the save files (single player), stats (multiplayer) are located.

For Windows XP:

C:\Program Files\Activision\Call of Duty 4 - Modern Warfare\players\profiles\"your profile name"

For Windows Vista:

C:\Users\"your vista account name"\AppData\Local\VirtualStore\Program Files\Activision\Call of Duty 4 - Modern Warfare\players\profiles\"your profile name"

• Get the Folder of your Profile name and not only the files inside, put it on a safe place first.
  
• start COD4 multiplayer create a profile with the same name as your previous/backed-up profile,
• Play a few rounds for the game to make your profile.
• Exit COD4 multiplayer then now you can copy the previous/backed-up profile over the newly created one.