If you see this screen during the optional installation:
Please wait until the system loads Emulationstation. You will be able to use the default setup without the additional emulators for the time being.
We will make a download available shortly that allows you to trigger the installation again from the desktop.
Advanced users can try now (attached keyboard necessary), like this:
From Emulationstation, open the Main Menu with "Start" on your controller or "F1" on the attached keyboard. Navigate to and select "Quit". Navigate to and select "Quit Emulationstation".
You will land in a command line shell.
Type: rm -r /RetrOrange* then press Enter.
Type: sudo retroengine/retrypie and press Enter.
Type: sudo reboot and press Enter. This will ask you for your administrator password. If you completed the Wifi Setup, your administrator password is identical to your Wifi password. Alternatively press P1 to power off, then reconnect power to restart.
Upon Reboot you can go through the Setup procedure again. Installed games should not be affected.