Reinstall GRUB?

[Doctor Who]

I recently added another hard drive to my machine.  Previously, I had
2 hard drives and Fedora was installed on one along with Vista.  I
installed grub to Fedora''s root and used a 3rd party boot loader to
access Fedora and other distros.

Now that the 3rd SATA drive is installed, Fedora's grub is messed up
because it's not on the drive it thinks it is (different order to
drives now).  How can I go about 'fixing' Fedora's grub entry and
re-installing grub to Fedora's root partition (not the MBR)?

Thanks.