Did you try to do this?
by R. Proffitt - 1/31/13 7:41 AM
In Reply to: How do i partition my 1TB HD which has just one volume ? by uditranjan18
And yes, for any reason we always have a backup of what we can't lose. Hard drives fail all the time and some folk are not prepared.
http://www.ubuntu.com/download/help/install-desktop-latest does not go into great detail but the last time I did that I did not have to partition the drive. I select the option to install Ubuntu alongside the install OS and the installer made the room for me.
Some folk don't try that and lose weeks or months trying to partition when if they had gone ahead and followed the directions they would have been done.