The installer will then download all the required packages and finally the system will reboot. If you installed from USB, you may be greeted with a blank screen with a single blinking cursor on reboot. This is because the installer has mistakenly installed grub on the USB drive instead of your HDD. To fix this, select the USB drive as boot drive on reboot - this will correctly launch Ubuntu. Log in with the username/password you created, and run the following to install grub on your real HDD...