I wanted to install Ubuntu on my notebook parallel to windows vista. But instead of three options, I could only choose between "replace windows vista" or "change partition".
Resizing and modyfing an existing system partition may be dangerous, but needs to be done if Windows occupy the whole hard disk. Therefore my guess is that you can do that only in manual partitioning mode when installing Ubuntu from the CD installer.
Alternatively, prepare some space for Ubuntu from Windows, using Settings -> Control Panel -> Administrative Tools -> Computer Management -> Storage -> Disk Management -> Shrink Volume. Ubuntu installer should notice that there is empty disk space that can be used for Ubuntu, and should give you the shoulder-to-shoulder option.