Check out
MSN Backup. This allows you to save not only the emoticons, but display pictures, winks, and just about everything else you might want to save.
Copy the folder all of that is saved into onto the other computer, then run the program again to import the files from where you saved them on the new computer.
Edit: It does not save the sounds, however, but you can do that by creating your own soundpack through the Plus! Sound Library interface on MSN Messenger itself. Then you just have to transfer that pack to the other computer.