I downloaded Apple Mac OS X Leopard iso file which is 7.5 GB. But it extracts only Bootcamp 403MB. What is it?

I downloaded Apple Mac OS X Leopard iso file which is 7.5 GB. But when I open that file with my burner or try to extract it, it shows only 403 MB. I made a disk and it has a setup of Bootcamp. What is it? Is it the whole Mac? Do I need to install only that. Plus it asks for XP or Vista. I use Windows 7. Plz help !!
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