Hi I recently put my leopard disc in my new mac mini and get nothing I went back and downloaded leopard to burn (I'm not a pirate I swear ) the file I get in the end is an ISO I burnt to my dl dvd in disc utillity but this disc didn't boot

Someone help these DL-DVDs are 5$ per disc and I can't afford to keep making files that won't boot, is it cause it's an ISO or I had the options wrong , someonenwalk me through please