I have downloaded 'manjaro-gnome-18.0.4-stable-x86_64.iso', and
the checksum was OK. Then, I made a bootable USB-Stick.
My system was Ubuntu 14 alongside Windows 7 (see attached image).
The 'Erase Disk' option offered, by default, a very convenient option, which was to remove everything and create a unique Manjaro operating system (see attached image).
The installation finished OK, and when rebooting, no operating system is detected