Obi: It means you will have to purchase an Operating System. You can normally purchase one as an added extra depending on the site you are buying your PC from. When you purchase an Operating System online, it will either come on a disk or USB, but, some websites may be able to just sell you the activation code. On the website you are buying your PC from, check to see if you are able to buy an operating system with it, just search "Windows" and one should come up.
You don't need to buy a computer without an operating system- if you don't know how to install one.
It does not work. You would then have to buy an operating system and install it. And then find correct drivers for all its hardware.
buy a builders disc from whereever, install it, and bam you are done I like 7 pro
but you can buy anything from xp to 10