If you have Linux on your second drive (not the primary one that the BIOS wants to boot from), it will automatically point the MBR on the first drive to the second (the BIOS will boot from the first drive but be directed to the second drive, where the GRUB executable files are, and then from GRUB be directed to either drive (depending on what you choose at the menu). If you want GRUB to be installed entirely on the second drive, you should set the BIOS to boot from the second drive first and then install GRUB and the MBR hook for it on HD2 using a live CD. I really don't see why you'd need to move it to HD2, as long as it gets to the GRUB menu and lets you pick which OS you want, that is what it is supposed to do.
