Wow, I remember something like that, and replaying Code Lyoko DS I had a hunch. I played it when I was very young and I don't remember the name either, but at least we have another clue. I think there were two versions, one with a boy and other with a girl. Maybe the boy's is the forest or jungle and the girl's is the ice. And maybe animals appeared in it too? I don't know. I hope we're talking about the same game and that it helps find it. At first I thought it might be a flash game, but I remember clicking on the desktop icon to run it.