Did you install Ubuntu directly to the hard drive from a CD or did you install Wubi (Wubi is the "Windows Ubuntu Installer" that allows you to install Ubuntu within Windows as if were a Windows program; it then presents a "choose Windows or Ubuntu" choice on boot up)?
I'm asking because you refer to "installing in drive D:\" in your post.
If the former, this link might help:
https://help.ubuntu.com/community/Grub2