It has a Windows 8.1 Professional System locked Preinstallation Key residing in the UEFI BIOS you do not need to purchase Windows 8.1, see here for details:

http://dellwindowsreinstallationguide.com/download-microsoft-windows-and-office/download-microsoft-windows/download-windows-8-1-retail-and-oem-iso/

P.S. I advise making the USB media and not using the DVD. DVDs have issues with the UEFI BIOS and SecureBoot.

As mentioned on the website it is an Unofficial Dell Windows Reinstallation Guide (I am the author). You can use the DVD but as I mentioned the USB will work better with UEFI and SecureBoot. To install Windows 8.1 you need to download media, adjust the UEFI BIOS settings and the clean install Windows. My guide is very detailed however.

Is this really the official way? I can't believe you have to go through that much effort to get Windows 8 on a laptop with Windows 8 sticker on it?

Why does it say software already installed on computer when it's in fact not.. and how does Dell expect us to use the cd when the laptop does not have a cd drive.. and there is nowhere a mention that you need to download something on Dell pages or support page..

Why does it say software already installed on computer when it's in fact not..

All the Reinstallation DVDs say that even the ones given when downgrade rights are used (a special case). I agree with you here that this is confusing...

and how does Dell expect us to use the cd when the laptop does not have a cd drive.. and there is nowhere a mention that you need to download something on Dell pages or support page..

This is why I write my own guides... The DVD is useless without an optical drive and even with a USB optical drive will likely be rejected by SecureBoot. A FAT32 Formatted USB Flash Drive will work. I've  also asked my Dell contacts why the Windows 8.1 Media Creation Tool isn't linked to in drivers and downloads.

Ok, so if I follow your guide, I have to reformat, which means that I lose the recovery partition and ability to reset to factory state?

any ideas about that last point?

Ok, so if I follow your guide, I have to reformat, which means that I lose the recovery partition and ability to reset to factory state?

Yes but you will make a new Windows 8.1 factory partition when you install Dell Backup and Recovery (after the system drivers).

Hm, but doesn't windows make a list of partitions upon install, which you can't change afterwards?

Dell Backup and Recovery will resize the Windows partition and make a recovery partition when it is installed on a clean installation.