I'm not familiar with the article you refer to, but Ubuntu should live happily side by side with Windows 7.
Take a look here at a tutorial I found searching via Google, which should give you a good insight into how to dual boot, but Ubuntu invariable does it all for you. Particularly if you chose to install from the live desktop icon.
Take a look at your Windows 7 disc manager and see if any hard drive space has been used by Ubuntu. It could be, it was simply running from the live CD/DVD and hasn't installed at all. Note: Windows won't be able to read that part of the hard drive and it will probably appear as unused space.
Alternatively, Ubuntu may not have installed a boot manager, which is the part of the jigsaw that gives you a dual boot option. But first seeing whether disc space has been used may provide a clue as to what happened.
Come back and let us know please.