How do I re install windows 7

Hi i have decided I don't like windows 8 and would like to do a clean re install of windows 7. how do I do it, if I start Win7 through win8 I don't get the clean install option, for that it tells me to boot the DVD and install that way, but the trouble is for some reason if I boot to the DVD the setup process just hangs at the win7 splash screen. how do I do a fresh clean re install of...