New Computer

I assume you're talking about CoD4 related files. I don't know how macs are organized, however I suppose the subfolders are the same for CoD4 on windows and on mac.
So the only important folder is the "player" folder. You can see more here: [TUT] Rank backup/transfer/restore in CoD4
If you want to avoid downloading all maps and mods again, you can also backup the "Mods" and "usermaps" folders.

The problem is, it only works if you keep the same key. If you change key, there is some manipulation to do to keep your ranks and stats (maybe someone else can help you, I never did it), otherwise your mpdata files will become corrupted.

Or maybe I'm totally off-topic and you weren't talking about CoD4 related files

Zitat von !nYpk!

Yeah I was talking about CoD
But you could give me my prestige and rank on my new cod key?

Sure np

if you have some time you can convert the mpdata files to the new ones.

The mpdata file is encrypted with your Key. When you start cod4 is uses your key to decrypt it.
There is a script by aluigi which decryptes a mpdata with your old key and encrypted it with a new one