1. Of course you can install Ubuntu on Hard Disk Drive D (I am not talking about
logical disk drive). While installing Ubuntu, it would
offer a page, in which you select the Hard Drive on which the OS
should be installed. This option is there in pretty much all the
operating system installers.
2. You can even install multiple operating systems on the same drive (D), the
bootloader corresponding to the last operating system which you install on that
drive will show up and list all the operating systems available on that drive.
3. You can read about sharing the swap space