Ubuntu from flash drive
There are instructions for creating a USB stick install of Ubuntu from Windows here: http://www.ubuntu.com/desktop/get-ubuntu/download
You are welcome to use USB stick for Ubuntu boot.
Just jump here: http://www.ubuntu.com/download/desktop
Choose the latest stable or the LTS, then the architecture, then download.
Follow the guide written here: http://www.ubuntu.com/download/help/create-a-usb-stick-on-windows
You are done!