BeOS!
So, today, I have decided to install BeOS R5. Having test driven BeOS for a month five years ago. I even got into using the BeOS users P2P file sharing network, where many BeOS software packages were available. I can't remember the name of it, but it seems the BeOS community is fully supportive of their favorite OS.
At the same time, I will be installing Haiku R1 Alpha 3. My goal is to port my media player to BeOS.