Follow this guide if you don’t know how to create and boot an Ubuntu live CD
The image you download from the Ubuntu website is a live-CD.
All you’ve got to do once downloaded is to burn it to disk by following the instructions which can also be found on the download page:
Once you have created the Ubuntu Live CD and it is booted, you can explore your local disk using their file manager and copy any files over.
You can also use the program to save all your files and folders if windows won’t start.