Alphie I get an error message stating my device is undetectable.
Probably it is best to pick one computer, so we can hold variables constant. Can you say which version of which OS, which version of which browser, and which cable you are using?
Also, since this has tripped other users up, when the device is in fastboot the word "start" will appear on the screen next to the power button. That does not mean that pressing the power button will start the installation (instead it will cancel).