In terms of not creating a new partition on your existing disk, I know of only three solutions:

• Install in a virtual machine -- You can use VirtualBox, VMWare, or similar software to install Ubuntu in a virtual environment under Windows. This usually works well, but there may be a performance penalty.


• Install on a separate disk -- You can install Ubuntu on a separate hard disk. (For a laptop, that's likely to be an external disk, but some laptops have bays for two hard disks.)


• Use WUBI -- This installs Ubuntu in a file on the Windows filesystem. This option, however, works only on BIOS-based computers, and IIRC, the developers are moving away from WUBI. Thus, it's not a real option for you unless your "UEFI" tag is a mistake, and even then it might not work in another release or two.

As a practical matter, your best solution is to be prepared with a complete system backup and a plan to restore it; then familiarize yourself with the installation procedure and the meanings of all the options, so that you can navigate it to do what you want. Unfortunately, the step-by-step guides that are so popular today do little to provide the sort of understanding that's needed for making meaningful decisions about your installation.