ElpaTech build a range of desktop PCs from basic to gaming. They have the naked PC as the default configuration and price and they have this to say about it:
The Allegro Forte does not come with an operating system pre-installed (sometimes referred to as a “naked PC”). This allows you to install whatever operating system you please. The operating system is the software that you use to interact with your computer; examples include Windows XP, Windows Vista and Ubuntu.
Top marks!
They don’t do laptops, but recommend Novatech, who are one of our few suppliers of naked laptops.
