I have a MacBook running OSX 5.8. I deleted the Mail application, because idiot. I want to reinstall it BUT the Install disk has OSX Version 5.5, so when I try and install from here it won't as there is a more recent version of OSX on teh computer. I don't want to go backwards to 10.5, I want to keep 10.5.8 and just add Mail. How do I do that then?