From version 4.0 onwards of the Kano Software, you'll be able to re-install the Software directly from the SD Card.
When the Kit boots up the following screen will show for 1-2 seconds. Press SHIFT to go into NOOBS Recovery Mode.
Next you will be greeted by the menu below. If you would like to reinstall the factory version of Kano OS, click Install and skip to Step 6. If you would like to reinstall the latest version of Kano OS, you will need an Internet connection. If the Kit is already connected via Ethernet, skip to Step 4.
Any Wi-Fi setup will need to be redone in this mode. Click Wifi networks and you will see the dialog below. Select your network from the list, input the password into the field, and click OK.
Once connected to the Internet, you will see Kano OS listed (may take a few seconds) from the SD card (this is the factory version) and once again from the Internet (shown by the Ethernet port icon).
Deselect the version from the SD card and only select the one from the Internet. Make sure only one box is ticked, otherwise you will have two OSs installed.
After this process, the entire OS will be reburned onto the SD card. Any personal files, documents, pictures etc. will be lost. Click Yes to confirm and begin.
If you're reinstalling the factory version from the SD card, this process might take around 10 minutes. Installing the latest Kano OS version will depend on your internet connection, typically 15-30 minutes.
Once everything is done the OS has been reinstalled. The dialog below will remain on the screen until you confirm.