My MacBook originally came with 10.4 in 2007. Recently I upgraded to 10.6... Now it's being very slow, so I want to downgrade it to 10.5 or 10.4. I don't have any disc that came with the machine purchase. I only have the 10.6 disc. How can I do this? I found 10.5 torrent online - would that work if I just burn it on a DVD to install? Or do I need something else?