My desktop OS: Zeta
In a world filled with alternative operating systems, sometimes you have to search for the best. Mac OS X? Nah. "Place name here" distribution of Linux? Nope. Zeta? Definitely. Zeta has all the power it needs to be my primary OS.
Zeta is based on the Be Operating System (BeOS). I have used BeOS since the free BeOS 5 Personal Edition was released in 2000, and its ease of use, quick boots, and minimal hardware requirements allowed BeOS to take full advantage of my computer, which had a 300MHz Celeron CPU, 64MB RAM, and 3dFX Voodoo 3 video adapter. Unfortunately, BeOS developer Be Inc. disbanded by the end of 2001, leaving an operating system that was unable to have more than 1GB of RAM, couldn't support up-to-date AMD and Intel CPUs without special boot disks, and lacked support for hard drives with more than 80GB of space and newer video cards.
Fortunately, a company called yellowTAB bought the rights to use the BeOS source code and began to develop Zeta. Those constraints on newer computers? Gone! For the most part, Zeta has worked on all the computers in my home, including the old 300MHz Celeron box, without fail, with nearly same speed BeOS had.