Windows 8.1 build 9600.16384 (winblue rtm)

Windows 8.1 build 9600 is the RTM of Windows 8.1.

Windows Classic in 8/8.1
You can get Windows Classic in Windows 8/8.1 without external software. To do so, right click on the desktop and click Personalization. Choose one of the high contrast themes and let it apply. Once done, click on Color and edit the settings as follows. Note: RGB is Red, Green, and Blue.

Windows Background: R: 255 G: 255 B: 255 Text: Black (or an RGB of 0, 0, and 0) Disabled Text: R: 128 G: 128 B: 128 Selected Text: Foreground: R: 255 G: 255 B: 255 Background: R: 10 G: 26 B: Active Window Title: Foreground: R: 255 G: 255 B: 255 Background R: 10 G: 36: B: 106 Inactive Window Title: Foreground: Black (or RGB 0) Background R: 128 G: 128 B: 128 Button: Foreground Black (or RGB 0) Background: R: 212 G: 208 B: 200

Once the settings are edited, save them, and you'll have a variant of the Windows Classic theme on Windows 8 and 8.1. This does not work on Windows 10.