I know there are a lot of tools to create a bootable usb for ubuntu with windows.
But I'm sure, that there was a possibility in the ubuntu installation directory. I used it some time ago, but I can't find it anymore :(
I think it was a .exe, or a .bat, any case a cmd window has opened, some things were executing and the usb was bootable. And it was in the ubuntu directory!
Is there still the possibility to do that? Does that file exist? I unfortunately can't remember.