Didn't watch the videos yet but I see that a public Windows 8 developer preview is now available.
In order to get the Windows 8 developer preview, just head on to
Microsoft's developer site and download it.
System requirements :
You'll just need a PC with a 1GHz or faster processor (either 32- or 64-bit), 1GB of RAM (2GB for 64-bit), 16GB of hard disk space (20GB for 64-bit), DirectX 9 graphics with WDDM 1.0 or higher driver. Of course, if you want to play with Windows 8's touch abilities, you'll need a screen that supports multi-touch.