Don't mix up 1) installation of the OS, 2) formatting. You need to learn these concepts first, just to understand what you are going to do. Installation of OS may or may not require formatting. I don't know exactly what kind of DVD you are using, so refer to the help or installation manual.
One of possible solutions would be: formatting the disk (make sure this is really what you want) could be done with any bootable utilities; many of them are based on Linux.
From the other hands, it's possible that you need not even formatting, but also re-partitioning and removing of the master boot (in all cases, you need to learn these concepts as well). But usually, OS installers can cope with all problems of disk preparation.
Apparently, installation of Windows 7 on a disk with Windows 8 is a distinct issue. Please see:
http://bit.ly/1l4L69n[
^].
In particular, please see these instructions:
http://www.pcmag.com/article2/0,2817,2417359,00.asp[
^].
—SA
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