To install on Windows, follow these steps. You will need admin permissions on your machine (at least for Windows XP). If you are on a school PC or other network where you have limited permissions and the installation below fails, you will need to talk to your system administrator.
Download and install the C++ libraries for Windows.
Download and install the OpenNI framework for Windows.
Download and install the Kinect OpenNI driver for Windows -- but see note below for Windows 8 and 10.
Download and install the NITE framework for Windows.
Download and install the sensor libraries for Windows.
If you are using Windows 8 or Windows 10, you will need to disable the Driver Signature Verification before installing the drivers. Press the windows key to bring up the start menu, and type "startup", then select "Change advanced start-up options" item which should appear. Click the "Restart Now" button. When it restarts and shows you a menu, select "Troubleshoot", then "Advanced Options" then "Startup Options" then "Restart". When Windows restarts again, it gives a numeric menu of options. Press 7 or F7 to select "Disable driver signing".
At this stage you can connect your Kinect to the PC. It may pop up and ask you about connecting to Windows update to look for drivers; say "No, not this time".
The software will attempt to install two devices, one will be for the Kinect audio and that will fail (but that's alright), the other will be for the Kinect camera and that should succeed. Then find your way to the directory
C:\Program Files\OpenNI\Samples\Bin\Release (for 32 bit Windows)
C:\Program Files (x86)\OpenNI\Samples\Bin\Release (for 64 bit Windows)
This should show a strange fuzzy black and white view in front of the sensor. Stand in front of it, and you should get drawn in a primary colour. If you adopt the calibration pose, it should show that you are calibrating, and then it should complete calibration and start drawing a stick-man skeletal structure on you. If you can't get this to work, don't bother going any further; if you have problems calibrating, check the lighting conditions in your room, the height of the sensor, the distance from you to the sensor.
If you are using Windows 8 or Windows 10, you should re-enable the Driver Signature Verification. Follow the earlier steps to enable driver verification again.
Assuming the sample works, there's only one more step to go: download and install the Kinect server. Once installed, run it using the shortcut "Greenfoot Kinect Server" in the start menu. If it runs successfully, after a few seconds you should see a little Greenfoot icon appear in your system tray (the area in the very bottom right, next to the time display). You can now try loading the Greenfoot scenario.