You can install it through windows.
If you have downloaded and got the .ISO file, then use an emulator to mount the disc and install through windows.
Disc emulators basically make your computer think it has another CD drive, when really it is just the program. The discs are the files from the disc, the .ISO or .CUE or whatever format it is in.
Daemon tools is about the best I have found so far because of how lightweight and easy to use it is
http://www.daemon-tools.cc/eng/downloads
light is the one that you want, install it (restart is needed before installation), then you will see a little icon in the bottom right with your other icons, a silver circle with a blue lightning bolt through. Left click it, click a device and find the Ubuntu file, click it, let it mount and autorun will run, run the installer, or, you can run the evaluator to use ubuntu through windows before you install it to see if you like it.
Alternatively, you can get a free ubuntu disc (which comes with stickers

) from here:
https://shipit.ubuntu.com/
It says up to 10 weeks but when i got mine it took a week and a little bit, and i got stickers

(did i mention that

)