In answer to your original question - not hard.

There are actually 2 ways to install Ubuntu along with Windows. There is a
file called wubi.exe on the Ubuntu (also Kubuntu, Xubuntu etc.) disk, which
you can run from within Windows to begin an Ubuntu installation. This
creates a large file with all of Ubuntu inside it. It is invisible to
Windows and you can choose from a new startup menu whether to start Windows
or Ubuntu. However, when installed this way there is a speed penalty.

The other option is to boot from the Ubuntu disk and choose the option to
install it alongside of Windows. This takes a lot longer because it has to
shrink the size of the Windows partition and create the Ubuntu installation
on it's own partition. Linux uses a different, incompatible, file system to
Windows. Again you choose from a startup menu and as long as you have
enough free space both work just fine, at full speed. Ubuntu will see the
Windows files but Windows won't see the Ubuntu install.

I suppose there is a third way, using a virtual machines - not the one from
Microsoft - to install Linux within Windows. You can do it the other way
around too and put Windows inside Ubuntu, which I do for those few
programmes that won't run under Wine in Ubuntu.

As for the failed driver installation... give it another try, it might
work. Make sure you have a solid internet connection and that the drivers
are really the right ones. Tell us more about why and what you were
installing and maybe someone here can give you some other options to try.