Windows Vista was like taking the design for a full-size sedan with a V8 engine and shrinking it down to a compact sedan, but *keeping* the overpowered V8 engine (even making it MORE powerful), and not improving the fuel efficiency.
Windows 7 was shrinking that V8 to a V6.
Windows 8/8.1 was shrinking the compact sedan to a 2-door, and making it a plug-in hybrid with a small displacement 4-cylinder.