Ubuntu will not load from any source on my various platforms

I have downloaded and burned ISO images to disk and USB, I have also downloaded ubuntu direct to 3 computers Windows 10, XP Pro SP3 and windows 7 laptop.
No installed app on any  of the computers is able to run the operating system, nor can I find anything online to do so.
Where on the various ISO downloaads and removeable media is the setup app that I can click on to run Ubuntu?
I,m about ready to give up on Linux!