First of all go into the bios and set the boot order of devices to 1.Dvd rom drive.
Set number two as the second drive in the list.
If you put the windows 7 disk in and it does not say press any key to boot from cd.
You do not have a boot able version of windows 7.
If you are at the point where it is about to install windows,but no hard drives are showing to install windows to, then the cause is the interface type used and may require a driver to be installed. Or you can go into the bios and change the interface type depending on how old the Pc is, for example if a Sata Hd, is not seen change the interface mode to Ahci mode instead. make sure you do not have secure boot enabled in the bios also as it will stop a fresh install of windows.