Ubuntu version 18.04 bootable USB drive (download zip file now 4.1GB) – this can be used to install Ubuntu on any computer – download and unzip to root of USB Drive and boot to usb drive.
You may also make a bootable Windows 10 USB drive using a windows 10 image file. Any windows key may be used including windows 7 to upgrade your computer to a windows 10 machine. Or use the Windows 10 USB bootable drive zip file – (download now 3.7GB)
Using your own iso file – create your own bootable usb drive using Rufus (download Portable version now 1.2Mb ) – extract the zip file and run rufus without installing.
Rufus is a utility that helps format and create bootable USB flash drives – web site
If you wish to install windows 10 on your Mac Computer, see this Website.