HamsterOS fits on just a single 1.44 MB floppy disk, and it's set for a full release this November.
It never became the next Unix, but after using it, I started seeing its fingerprints in places I already use.
You may view your hard drive in Disk Management and see unallocated space. The space will be on the hard drive, but Windows cannot use it. It is like having a spare room in your house but locked off.