It's not clear whether you are trying to install the game on your new computer or simply move savegames. If you want to move your savegames to your new computer, you can find out how to do that in this post.

If you're trying to install the game on your new computer, the procedure depends upon where you purchased the game. This post has some general instructions. If you still have the downloaded install file on your other computer, you can put that on a CD and use it to install the game on your new computer. Otherwise, you'll have to download it again.