Scientific Linux 7.0 / 7.1 Alpha
https://www.scientificlinux.org/
Scientific Linux 6 is the newest branch of this Red Hat Enterprise Linux based operating system designed for scientists. It is an open source distribution of Linux that comes pre-installed with two main desktop environments, as well as a plethora of libre tools and applications designed for scientists.
Available for download as installable-only DVDs for mainstream platforms

The base distribution is basically Red Hat Enterprise Linux 6.x, recompiled from the publicly available source packages. This means that it uses the RPM Package Management system for installation, update or removal of packages from the system.

This edition is available for download as installable-only DVD ISO images of approximately 4GB in size each, suitable for either 32-bit (i386) or 64-bit (x86_64) hardware platforms.

Keep in mind though, that there are two DVD ISO images for each architecture, but you only need to download the first disc for a basic installation, as the second one includes extra applications.
Easy to follow boot instructions and a straightforward installation