Lol predator, when u install COD4, it adds something to your registry about where ur game is located and your key, also the game version. Prolly more but i cannot name them all.
Just Start>Run>regedit *enter* - Open local machine>Software>Activision, right mouse click on that and use ''Export..'' then u can save it where u want.
Dubble click on your key to change that and just put it back after the save, or leave it i wont use it anyway.
Then u could just upload it on a attachment too a PM or this post.
I hope u can do that for me, will only take a minute