From Dell you can but it will cost you about $200-300 more to get it from dell
This is a great question and certainly is a complex one as well! As it turns out, this computer’s operating system cannot be changed to Windows 7 64-bit before purchase, since it has been built by Dell with Windows 8 64-bit already pre-installed. Microsoft does offer software downgrade rights to certain systems ordered from Dell that were configured with Windows 8 Pro 64-bit OS from the factory. You can learn more about this here:
That said, you are also free to purchase your own copy of Windows 7 64-bit and install it on this computer if you wish. I do recommend keeping the existing Windows 8 OS installed on its own partition and installing Windows 7 onto a separate partition. This is so if you need to call into Dell Support for any issue, they will need to work from within the Windows 8 environment, since that is how Dell originally configured the computer.
Luckily, this system has specific drivers available from Dell that helps it run Windows 7 correctly, so be sure to grab those from support.dell.com to help finalize your install. Also, certain newer systems have what’s called Secure Boot in the BIOS, which may need to be disabled before you install Windows 7. There is an article about this here:
Hope this helps!