I also agree that there is little reason to remove WIN 8 which is already pre-installed, unless disc space is that much of an issue. I understand that some existing programs will not work with WIN 8, one of my favorite utilities being one of them, with no further development planned.

Since you already have the WIN 7 install discs, and a license key, then why not just install it as dual-boot? You can just set it to boot automatically into WIN 7, so don't even have to go into WIN 8 if you chose not to. And the only difference is that during boot up, you're given a choice which OS to start up.
Note that you generally cannot use WIN 7 install discs from another manufacturer as they are customized for specific hardware. Unless it's a separate Microsoft Windows 7 disc. However, a moot point, as you can download(?) most versions of Windows 7 .iso files and burn it to a single DVD. The exception being Window 7 Starter disc which is not available, but could make your own Starter install disc from most any other Windows 7 version disc. It involves just modifying a config file to tell which version of WIN 7 to install. You still need a valid WIN 7 license key for the version you plan to use.