Are you signed up for the PTS? That is a mirror of the game and uninstalling that will free up an equal amount of HDD space.
There are also some things you can do to free up your HDD space. Moving My Documents, Temp Files, Temp Internet Files, Mozilla Profiles and the like to another drive to another drive. Obviously you could uninstall some other things your not using. If your using an SSD, you want to do this anyway. It will make the drive last longer.
Also, if your using Steam, it is real easy to move that to another drive, so you could buy a new drive install that, and then move Steam. On my rig, that would be 100's of GB of space.