I agree that your best bet is to do a regular Ubuntu
installation. WUBI is not meant to be a replacement for it. WUBI is meant to
give a try before you install experience that is better than a Live CD and
not for your main operating system. There are good reasons not to rely on
WUBI for your main OS. WUBI is hosted on the Windows operating system even
though it does not rely on Windows to run and is subject to problems that it
may encounter, such as fragmentation slowing down things and virus
infections which would not normally affect Linux. The virus would not get
into Linux, but some viruses or trojans are nasty enough to mean that you
have to wipe the drive or they could mess with the boot sector.
Insert the disk in the drive and boot the computer. Then run the installer.
When Ubuntu installs choose to share the drive with Windows and not to use
the entire drive. You can accept most defaults, although you can get a
better setup if you do a custom installation and partition things yourself,
but that can wait till you have more experience. If you want to do that now,
it isn't hard, especially if your Windows is new and if you make a mistake
it will likely mean that you will have to start over at worst.
A separate partition for Ubuntu would look different from WUBI because you
would see a different screen when you re-boot. WUBI uses Windows' bootloader
and Ubuntu uses grub. You will have more choices and Ubuntu would be the
default choice instead of Windows. Also if you have a laptop then suspend
should now work from Ubuntu. WUBI cannot handle suspend due to the way it
loads.