How to download microsoft 2007 on a macbook?

i have a 10.5.8 macbook and a microsoft ofice 2007 disk. i want to download microsoft office 2007 on my macbook, but when i put the disk in, a icon forms on the desktop called office12. I click on office 12 and it has all these files like setup.exe, and word.exe. I know that this disk is authentic because i bought it myself, used it on systems with microsoft, but never on a mac. thank you for your time. i will award the best answer personally.